diff --git a/src/main/java/io/reactivex/internal/disposables/EmptyDisposable.java b/src/main/java/io/reactivex/internal/disposables/EmptyDisposable.java
index f9cc1ef2da..4ac0d33dbf 100644
--- a/src/main/java/io/reactivex/internal/disposables/EmptyDisposable.java
+++ b/src/main/java/io/reactivex/internal/disposables/EmptyDisposable.java
@@ -14,6 +14,7 @@
 package io.reactivex.internal.disposables;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.internal.fuseable.QueueDisposable;
 
 /**
@@ -93,6 +94,7 @@ public boolean offer(Object v1, Object v2) {
         throw new UnsupportedOperationException("Should not be called!");
     }
 
+    @Nullable
     @Override
     public Object poll() throws Exception {
         return null; // always empty
diff --git a/src/main/java/io/reactivex/internal/fuseable/SimplePlainQueue.java b/src/main/java/io/reactivex/internal/fuseable/SimplePlainQueue.java
index fa521f694a..c2cdff7700 100644
--- a/src/main/java/io/reactivex/internal/fuseable/SimplePlainQueue.java
+++ b/src/main/java/io/reactivex/internal/fuseable/SimplePlainQueue.java
@@ -13,6 +13,8 @@
 
 package io.reactivex.internal.fuseable;
 
+import io.reactivex.annotations.Nullable;
+
 /**
  * Override of the SimpleQueue interface with no throws Exception on poll.
  *
@@ -20,6 +22,7 @@
  */
 public interface SimplePlainQueue<T> extends SimpleQueue<T> {
 
+    @Nullable
     @Override
     T poll();
 }
diff --git a/src/main/java/io/reactivex/internal/fuseable/SimpleQueue.java b/src/main/java/io/reactivex/internal/fuseable/SimpleQueue.java
index 0280924910..6a59328c7f 100644
--- a/src/main/java/io/reactivex/internal/fuseable/SimpleQueue.java
+++ b/src/main/java/io/reactivex/internal/fuseable/SimpleQueue.java
@@ -13,6 +13,8 @@
 
 package io.reactivex.internal.fuseable;
 
+import io.reactivex.annotations.Nullable;
+
 /**
  * A minimalist queue interface without the method bloat of java.util.Collection and java.util.Queue.
  *
@@ -24,6 +26,10 @@ public interface SimpleQueue<T> {
 
     boolean offer(T v1, T v2);
 
+    /**
+     * @return null to indicate an empty queue
+     */
+    @Nullable
     T poll() throws Exception;
 
     boolean isEmpty();
diff --git a/src/main/java/io/reactivex/internal/observers/DeferredScalarDisposable.java b/src/main/java/io/reactivex/internal/observers/DeferredScalarDisposable.java
index f666cec7d4..8dd5084d7e 100644
--- a/src/main/java/io/reactivex/internal/observers/DeferredScalarDisposable.java
+++ b/src/main/java/io/reactivex/internal/observers/DeferredScalarDisposable.java
@@ -14,6 +14,7 @@
 package io.reactivex.internal.observers;
 
 import io.reactivex.Observer;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.plugins.RxJavaPlugins;
 
 /**
@@ -110,6 +111,7 @@ public final void complete() {
         actual.onComplete();
     }
 
+    @Nullable
     @Override
     public final T poll() throws Exception {
         if (get() == FUSED_READY) {
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableCombineLatest.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableCombineLatest.java
index 14b1366840..30c9443319 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableCombineLatest.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableCombineLatest.java
@@ -16,6 +16,7 @@
 import java.util.Iterator;
 import java.util.concurrent.atomic.*;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.Flowable;
@@ -466,6 +467,7 @@ public int requestFusion(int requestedMode) {
             return m;
         }
 
+        @Nullable
         @SuppressWarnings("unchecked")
         @Override
         public R poll() throws Exception {
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableDistinct.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableDistinct.java
index 5f8cf26ebd..67e83448af 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableDistinct.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableDistinct.java
@@ -16,6 +16,7 @@
 import java.util.Collection;
 import java.util.concurrent.Callable;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.exceptions.Exceptions;
@@ -117,6 +118,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             for (;;) {
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableDistinctUntilChanged.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableDistinctUntilChanged.java
index 7cb1a19eea..6db754560e 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableDistinctUntilChanged.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableDistinctUntilChanged.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.operators.flowable;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.functions.*;
@@ -106,6 +107,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             for (;;) {
@@ -195,6 +197,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             for (;;) {
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoAfterNext.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoAfterNext.java
index 8d2485946a..1960e246ef 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoAfterNext.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoAfterNext.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.operators.flowable;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.annotations.Experimental;
@@ -74,6 +75,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             T v = qs.poll();
@@ -122,6 +124,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             T v = qs.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoFinally.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoFinally.java
index 567ee2845b..e31ac375ae 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoFinally.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoFinally.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.operators.flowable;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.annotations.Experimental;
@@ -130,6 +131,7 @@ public boolean isEmpty() {
             return qs.isEmpty();
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             T v = qs.poll();
@@ -239,6 +241,7 @@ public boolean isEmpty() {
             return qs.isEmpty();
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             T v = qs.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoOnEach.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoOnEach.java
index 847eefa774..b8a6b4f513 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoOnEach.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableDoOnEach.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.operators.flowable;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.exceptions.*;
@@ -144,6 +145,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             T v = qs.poll();
@@ -276,6 +278,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             T v = qs.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableFilter.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableFilter.java
index ec0d23278d..c326e6e623 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableFilter.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableFilter.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.operators.flowable;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.functions.Predicate;
@@ -79,6 +80,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             QueueSubscription<T> qs = this.qs;
@@ -143,6 +145,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             QueueSubscription<T> qs = this.qs;
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableFlatMapCompletable.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableFlatMapCompletable.java
index 18b02a140d..940180680c 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableFlatMapCompletable.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableFlatMapCompletable.java
@@ -15,6 +15,7 @@
 
 import java.util.concurrent.atomic.AtomicReference;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.*;
@@ -174,6 +175,7 @@ public void request(long n) {
             // ignored, no values emitted
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             return null; // always empty
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableFlattenIterable.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableFlattenIterable.java
index e3fc03dcd1..fd97b5bfcc 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableFlattenIterable.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableFlattenIterable.java
@@ -17,6 +17,7 @@
 import java.util.concurrent.Callable;
 import java.util.concurrent.atomic.*;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.exceptions.*;
@@ -413,6 +414,7 @@ public boolean isEmpty() {
             return (it != null && !it.hasNext()) || queue.isEmpty();
         }
 
+        @Nullable
         @Override
         public R poll() throws Exception {
             Iterator<? extends R> it = current;
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableFromArray.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableFromArray.java
index 8ebfdedc4f..51886f8650 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableFromArray.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableFromArray.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.operators.flowable;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.Subscriber;
 
 import io.reactivex.Flowable;
@@ -55,6 +56,7 @@ public final int requestFusion(int mode) {
             return mode & SYNC;
         }
 
+        @Nullable
         @Override
         public final T poll() {
             int i = index;
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableFromIterable.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableFromIterable.java
index 584cc08b4d..56c4b6c05b 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableFromIterable.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableFromIterable.java
@@ -15,6 +15,7 @@
 
 import java.util.Iterator;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.Subscriber;
 
 import io.reactivex.Flowable;
@@ -87,6 +88,7 @@ public final int requestFusion(int mode) {
             return mode & SYNC;
         }
 
+        @Nullable
         @Override
         public final T poll() {
             if (it == null) {
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableGroupBy.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableGroupBy.java
index e4582e587b..649d2b9d35 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableGroupBy.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableGroupBy.java
@@ -17,6 +17,7 @@
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.*;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.exceptions.Exceptions;
@@ -353,6 +354,7 @@ public int requestFusion(int mode) {
             return NONE;
         }
 
+        @Nullable
         @Override
         public GroupedFlowable<K, V> poll() {
             return queue.poll();
@@ -627,6 +629,7 @@ public int requestFusion(int mode) {
             return NONE;
         }
 
+        @Nullable
         @Override
         public T poll() {
             T v = queue.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableIgnoreElements.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableIgnoreElements.java
index 4d8a90a5cd..d2d7979285 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableIgnoreElements.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableIgnoreElements.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.operators.flowable;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.internal.fuseable.QueueSubscription;
@@ -72,6 +73,7 @@ public boolean offer(T v1, T v2) {
             throw new UnsupportedOperationException("Should not be called!");
         }
 
+        @Nullable
         @Override
         public T poll() {
             return null; // empty, always
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableMap.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableMap.java
index dcefbd32ab..e168d84ecb 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableMap.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableMap.java
@@ -14,6 +14,7 @@
 
 package io.reactivex.internal.operators.flowable;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.functions.Function;
@@ -72,6 +73,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public U poll() throws Exception {
             T t = qs.poll();
@@ -131,6 +133,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public U poll() throws Exception {
             T t = qs.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableObserveOn.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableObserveOn.java
index 726c0716e9..d50339b2be 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableObserveOn.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableObserveOn.java
@@ -15,6 +15,7 @@
 
 import java.util.concurrent.atomic.AtomicLong;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.Scheduler;
@@ -457,6 +458,7 @@ void runBackfused() {
             }
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             T v = queue.poll();
@@ -695,6 +697,7 @@ void runBackfused() {
             }
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             T v = queue.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableOnBackpressureBuffer.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableOnBackpressureBuffer.java
index 4275473a19..ec20946b85 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableOnBackpressureBuffer.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableOnBackpressureBuffer.java
@@ -15,6 +15,7 @@
 
 import java.util.concurrent.atomic.AtomicLong;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.exceptions.*;
@@ -251,6 +252,7 @@ public int requestFusion(int mode) {
             return NONE;
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             return queue.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableRange.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableRange.java
index 794b309938..8811b899aa 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableRange.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableRange.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.operators.flowable;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.Subscriber;
 
 import io.reactivex.Flowable;
@@ -59,6 +60,7 @@ public final int requestFusion(int mode) {
             return mode & SYNC;
         }
 
+        @Nullable
         @Override
         public final Integer poll() {
             int i = index;
diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableRangeLong.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableRangeLong.java
index f9f2fcd286..c2188e5603 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableRangeLong.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableRangeLong.java
@@ -14,6 +14,7 @@
 package io.reactivex.internal.operators.flowable;
 
 import io.reactivex.Flowable;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.internal.fuseable.ConditionalSubscriber;
 import io.reactivex.internal.subscriptions.BasicQueueSubscription;
 import io.reactivex.internal.subscriptions.SubscriptionHelper;
@@ -62,6 +63,7 @@ public final int requestFusion(int mode) {
             return mode & SYNC;
         }
 
+        @Nullable
         @Override
         public final Long poll() {
             long i = index;
diff --git a/src/main/java/io/reactivex/internal/operators/maybe/MaybeFlatMapIterableFlowable.java b/src/main/java/io/reactivex/internal/operators/maybe/MaybeFlatMapIterableFlowable.java
index 50b653ffdb..783e254613 100644
--- a/src/main/java/io/reactivex/internal/operators/maybe/MaybeFlatMapIterableFlowable.java
+++ b/src/main/java/io/reactivex/internal/operators/maybe/MaybeFlatMapIterableFlowable.java
@@ -16,6 +16,7 @@
 import java.util.Iterator;
 import java.util.concurrent.atomic.AtomicLong;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.Subscriber;
 
 import io.reactivex.*;
@@ -277,6 +278,7 @@ public boolean isEmpty() {
             return it == null;
         }
 
+        @Nullable
         @Override
         public R poll() throws Exception {
             Iterator<? extends R> iter = it;
diff --git a/src/main/java/io/reactivex/internal/operators/maybe/MaybeFlatMapIterableObservable.java b/src/main/java/io/reactivex/internal/operators/maybe/MaybeFlatMapIterableObservable.java
index 167b41ed3b..af3027ca00 100644
--- a/src/main/java/io/reactivex/internal/operators/maybe/MaybeFlatMapIterableObservable.java
+++ b/src/main/java/io/reactivex/internal/operators/maybe/MaybeFlatMapIterableObservable.java
@@ -16,6 +16,7 @@
 import java.util.Iterator;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.disposables.Disposable;
 import io.reactivex.exceptions.Exceptions;
 import io.reactivex.functions.Function;
@@ -187,6 +188,7 @@ public boolean isEmpty() {
             return it == null;
         }
 
+        @Nullable
         @Override
         public R poll() throws Exception {
             Iterator<? extends R> iter = it;
diff --git a/src/main/java/io/reactivex/internal/operators/maybe/MaybeMergeArray.java b/src/main/java/io/reactivex/internal/operators/maybe/MaybeMergeArray.java
index e256f5ee7f..a012deecf8 100644
--- a/src/main/java/io/reactivex/internal/operators/maybe/MaybeMergeArray.java
+++ b/src/main/java/io/reactivex/internal/operators/maybe/MaybeMergeArray.java
@@ -16,6 +16,7 @@
 import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.atomic.*;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.Subscriber;
 
 import io.reactivex.*;
@@ -107,6 +108,7 @@ public int requestFusion(int mode) {
             return NONE;
         }
 
+        @Nullable
         @SuppressWarnings("unchecked")
         @Override
         public T poll() throws Exception {
@@ -299,6 +301,7 @@ void drain() {
 
     interface SimpleQueueWithConsumerIndex<T> extends SimpleQueue<T> {
 
+        @Nullable
         @Override
         T poll();
 
@@ -342,6 +345,7 @@ public boolean offer(T v1, T v2) {
             throw new UnsupportedOperationException();
         }
 
+        @Nullable
         @Override
         public T poll() {
             int ci = consumerIndex;
@@ -422,6 +426,7 @@ public boolean offer(T e) {
             return super.offer(e);
         }
 
+        @Nullable
         @Override
         public T poll() {
             T v = super.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableDistinct.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableDistinct.java
index 1122d0b6c9..4e625ee44c 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableDistinct.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableDistinct.java
@@ -17,6 +17,7 @@
 import java.util.concurrent.Callable;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.exceptions.Exceptions;
 import io.reactivex.functions.Function;
 import io.reactivex.internal.disposables.EmptyDisposable;
@@ -113,6 +114,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             for (;;) {
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableDistinctUntilChanged.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableDistinctUntilChanged.java
index 28f8e97d48..0267ad68e3 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableDistinctUntilChanged.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableDistinctUntilChanged.java
@@ -14,6 +14,7 @@
 package io.reactivex.internal.operators.observable;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.functions.*;
 import io.reactivex.internal.observers.BasicFuseableObserver;
 
@@ -90,6 +91,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             for (;;) {
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableDoAfterNext.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableDoAfterNext.java
index aa2756fadd..dc01638d96 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableDoAfterNext.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableDoAfterNext.java
@@ -15,6 +15,7 @@
 
 import io.reactivex.*;
 import io.reactivex.annotations.Experimental;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.functions.Consumer;
 import io.reactivex.internal.observers.BasicFuseableObserver;
 
@@ -65,6 +66,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             T v = qs.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableDoFinally.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableDoFinally.java
index 6a9de088fe..cf474c164d 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableDoFinally.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableDoFinally.java
@@ -15,6 +15,7 @@
 
 import io.reactivex.*;
 import io.reactivex.annotations.Experimental;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.disposables.Disposable;
 import io.reactivex.exceptions.Exceptions;
 import io.reactivex.functions.Action;
@@ -127,6 +128,7 @@ public boolean isEmpty() {
             return qd.isEmpty();
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             T v = qd.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableFilter.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableFilter.java
index d025980114..108c44a88c 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableFilter.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableFilter.java
@@ -14,6 +14,7 @@
 package io.reactivex.internal.operators.observable;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.functions.Predicate;
 import io.reactivex.internal.observers.BasicFuseableObserver;
 
@@ -60,6 +61,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             for (;;) {
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableFlatMapCompletable.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableFlatMapCompletable.java
index 1b1ee95ae9..428d54e0d7 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableFlatMapCompletable.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableFlatMapCompletable.java
@@ -16,6 +16,7 @@
 import java.util.concurrent.atomic.AtomicReference;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.disposables.*;
 import io.reactivex.exceptions.Exceptions;
 import io.reactivex.functions.Function;
@@ -148,6 +149,7 @@ public boolean isDisposed() {
             return d.isDisposed();
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             return null; // always empty
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableFromArray.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableFromArray.java
index ed20375b76..4ac881ceec 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableFromArray.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableFromArray.java
@@ -14,6 +14,7 @@
 package io.reactivex.internal.operators.observable;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.internal.functions.ObjectHelper;
 import io.reactivex.internal.observers.BasicQueueDisposable;
 
@@ -61,6 +62,7 @@ public int requestFusion(int mode) {
             return NONE;
         }
 
+        @Nullable
         @Override
         public T poll() {
             int i = index;
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableFromIterable.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableFromIterable.java
index be8e95923a..3a8b7853d5 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableFromIterable.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableFromIterable.java
@@ -16,6 +16,7 @@
 import java.util.Iterator;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.exceptions.Exceptions;
 import io.reactivex.internal.disposables.EmptyDisposable;
 import io.reactivex.internal.functions.ObjectHelper;
@@ -122,6 +123,7 @@ public int requestFusion(int mode) {
             return NONE;
         }
 
+        @Nullable
         @Override
         public T poll() {
             if (done) {
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableMap.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableMap.java
index dff47794f6..caed356c01 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableMap.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableMap.java
@@ -15,6 +15,7 @@
 package io.reactivex.internal.operators.observable;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.functions.Function;
 import io.reactivex.internal.functions.ObjectHelper;
 import io.reactivex.internal.observers.BasicFuseableObserver;
@@ -68,6 +69,7 @@ public int requestFusion(int mode) {
             return transitiveBoundaryFusion(mode);
         }
 
+        @Nullable
         @Override
         public U poll() throws Exception {
             T t = qs.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableObserveOn.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableObserveOn.java
index f2174f97a8..08443bbd2f 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableObserveOn.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableObserveOn.java
@@ -14,6 +14,7 @@
 package io.reactivex.internal.operators.observable;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.disposables.Disposable;
 import io.reactivex.exceptions.Exceptions;
 import io.reactivex.internal.disposables.DisposableHelper;
@@ -294,6 +295,7 @@ public int requestFusion(int mode) {
             return NONE;
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             return queue.poll();
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableRange.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableRange.java
index d5fda984f2..2718ef6c8e 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableRange.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableRange.java
@@ -13,6 +13,7 @@
 package io.reactivex.internal.operators.observable;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.internal.observers.BasicIntQueueDisposable;
 
 /**
@@ -68,6 +69,7 @@ void run() {
             }
         }
 
+        @Nullable
         @Override
         public Integer poll() throws Exception {
             long i = index;
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableRangeLong.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableRangeLong.java
index 7e49b6e65f..851a5ecea3 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableRangeLong.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableRangeLong.java
@@ -13,6 +13,7 @@
 package io.reactivex.internal.operators.observable;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.internal.observers.BasicIntQueueDisposable;
 
 public final class ObservableRangeLong extends Observable<Long> {
@@ -65,6 +66,7 @@ void run() {
             }
         }
 
+        @Nullable
         @Override
         public Long poll() throws Exception {
             long i = index;
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableScalarXMap.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableScalarXMap.java
index 3833565af7..418e6514f9 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableScalarXMap.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableScalarXMap.java
@@ -17,6 +17,7 @@
 import java.util.concurrent.atomic.AtomicInteger;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.exceptions.Exceptions;
 import io.reactivex.functions.Function;
 import io.reactivex.internal.disposables.EmptyDisposable;
@@ -202,6 +203,7 @@ public boolean offer(T v1, T v2) {
             throw new UnsupportedOperationException("Should not be called!");
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             if (get() == FUSED) {
diff --git a/src/main/java/io/reactivex/internal/operators/single/SingleFlatMapIterableFlowable.java b/src/main/java/io/reactivex/internal/operators/single/SingleFlatMapIterableFlowable.java
index ab07b5e1a4..4bc10136b9 100644
--- a/src/main/java/io/reactivex/internal/operators/single/SingleFlatMapIterableFlowable.java
+++ b/src/main/java/io/reactivex/internal/operators/single/SingleFlatMapIterableFlowable.java
@@ -16,6 +16,7 @@
 import java.util.Iterator;
 import java.util.concurrent.atomic.AtomicLong;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.Subscriber;
 
 import io.reactivex.*;
@@ -271,6 +272,7 @@ public boolean isEmpty() {
             return it == null;
         }
 
+        @Nullable
         @Override
         public R poll() throws Exception {
             Iterator<? extends R> iter = it;
diff --git a/src/main/java/io/reactivex/internal/operators/single/SingleFlatMapIterableObservable.java b/src/main/java/io/reactivex/internal/operators/single/SingleFlatMapIterableObservable.java
index 8e670350b6..c93a55af9e 100644
--- a/src/main/java/io/reactivex/internal/operators/single/SingleFlatMapIterableObservable.java
+++ b/src/main/java/io/reactivex/internal/operators/single/SingleFlatMapIterableObservable.java
@@ -16,6 +16,7 @@
 import java.util.Iterator;
 
 import io.reactivex.*;
+import io.reactivex.annotations.Nullable;
 import io.reactivex.disposables.Disposable;
 import io.reactivex.exceptions.Exceptions;
 import io.reactivex.functions.Function;
@@ -181,6 +182,7 @@ public boolean isEmpty() {
             return it == null;
         }
 
+        @Nullable
         @Override
         public R poll() throws Exception {
             Iterator<? extends R> iter = it;
diff --git a/src/main/java/io/reactivex/internal/queue/MpscLinkedQueue.java b/src/main/java/io/reactivex/internal/queue/MpscLinkedQueue.java
index bcaff38358..eddfb306b4 100644
--- a/src/main/java/io/reactivex/internal/queue/MpscLinkedQueue.java
+++ b/src/main/java/io/reactivex/internal/queue/MpscLinkedQueue.java
@@ -20,6 +20,7 @@
 
 import java.util.concurrent.atomic.AtomicReference;
 
+import io.reactivex.annotations.Nullable;
 import io.reactivex.internal.fuseable.SimplePlainQueue;
 
 /**
@@ -81,6 +82,7 @@ public boolean offer(final T e) {
      *
      * @see java.util.Queue#poll()
      */
+    @Nullable
     @Override
     public T poll() {
         LinkedQueueNode<T> currConsumerNode = lpConsumerNode(); // don't load twice, it's alright
diff --git a/src/main/java/io/reactivex/internal/queue/SpscArrayQueue.java b/src/main/java/io/reactivex/internal/queue/SpscArrayQueue.java
index 7e85034fd4..1afa99738f 100644
--- a/src/main/java/io/reactivex/internal/queue/SpscArrayQueue.java
+++ b/src/main/java/io/reactivex/internal/queue/SpscArrayQueue.java
@@ -20,6 +20,7 @@
 
 import java.util.concurrent.atomic.*;
 
+import io.reactivex.annotations.Nullable;
 import io.reactivex.internal.fuseable.SimplePlainQueue;
 import io.reactivex.internal.util.Pow2;
 
@@ -82,6 +83,7 @@ public boolean offer(E v1, E v2) {
         return offer(v1) && offer(v2);
     }
 
+    @Nullable
     @Override
     public E poll() {
         final long index = consumerIndex.get();
diff --git a/src/main/java/io/reactivex/internal/queue/SpscLinkedArrayQueue.java b/src/main/java/io/reactivex/internal/queue/SpscLinkedArrayQueue.java
index 33bbba45ae..f386ac998f 100644
--- a/src/main/java/io/reactivex/internal/queue/SpscLinkedArrayQueue.java
+++ b/src/main/java/io/reactivex/internal/queue/SpscLinkedArrayQueue.java
@@ -20,6 +20,7 @@
 
 import java.util.concurrent.atomic.*;
 
+import io.reactivex.annotations.Nullable;
 import io.reactivex.internal.fuseable.SimplePlainQueue;
 import io.reactivex.internal.util.Pow2;
 
@@ -121,6 +122,7 @@ private AtomicReferenceArray<Object> lvNext(AtomicReferenceArray<Object> curr) {
      * <p>
      * This implementation is correct for single consumer thread use only.
      */
+    @Nullable
     @SuppressWarnings("unchecked")
     @Override
     public T poll() {
diff --git a/src/main/java/io/reactivex/internal/subscriptions/DeferredScalarSubscription.java b/src/main/java/io/reactivex/internal/subscriptions/DeferredScalarSubscription.java
index d142415049..3e0406f4fe 100644
--- a/src/main/java/io/reactivex/internal/subscriptions/DeferredScalarSubscription.java
+++ b/src/main/java/io/reactivex/internal/subscriptions/DeferredScalarSubscription.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.subscriptions;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.Subscriber;
 
 /**
@@ -156,6 +157,7 @@ public final int requestFusion(int mode) {
         return NONE;
     }
 
+    @Nullable
     @Override
     public final T poll() {
         if (get() == FUSED_READY) {
diff --git a/src/main/java/io/reactivex/internal/subscriptions/EmptySubscription.java b/src/main/java/io/reactivex/internal/subscriptions/EmptySubscription.java
index 7210449a70..08fd1faae8 100644
--- a/src/main/java/io/reactivex/internal/subscriptions/EmptySubscription.java
+++ b/src/main/java/io/reactivex/internal/subscriptions/EmptySubscription.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.subscriptions;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.Subscriber;
 
 import io.reactivex.internal.fuseable.QueueSubscription;
@@ -66,6 +67,7 @@ public static void complete(Subscriber<?> s) {
         s.onSubscribe(INSTANCE);
         s.onComplete();
     }
+    @Nullable
     @Override
     public Object poll() {
         return null; // always empty
diff --git a/src/main/java/io/reactivex/internal/subscriptions/ScalarSubscription.java b/src/main/java/io/reactivex/internal/subscriptions/ScalarSubscription.java
index 2a8a33dcd9..d16484c31a 100644
--- a/src/main/java/io/reactivex/internal/subscriptions/ScalarSubscription.java
+++ b/src/main/java/io/reactivex/internal/subscriptions/ScalarSubscription.java
@@ -15,6 +15,7 @@
 
 import java.util.concurrent.atomic.AtomicInteger;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.Subscriber;
 
 import io.reactivex.internal.fuseable.QueueSubscription;
@@ -82,6 +83,7 @@ public boolean offer(T v1, T v2) {
         throw new UnsupportedOperationException("Should not be called!");
     }
 
+    @Nullable
     @Override
     public T poll() {
         if (get() == NO_REQUEST) {
diff --git a/src/main/java/io/reactivex/processors/UnicastProcessor.java b/src/main/java/io/reactivex/processors/UnicastProcessor.java
index 68ef48e6ed..ecd624da8c 100644
--- a/src/main/java/io/reactivex/processors/UnicastProcessor.java
+++ b/src/main/java/io/reactivex/processors/UnicastProcessor.java
@@ -16,6 +16,7 @@
 import io.reactivex.annotations.CheckReturnValue;
 import java.util.concurrent.atomic.*;
 
+import io.reactivex.annotations.Nullable;
 import org.reactivestreams.*;
 
 import io.reactivex.internal.functions.ObjectHelper;
@@ -340,6 +341,7 @@ final class UnicastQueueSubscription extends BasicIntQueueSubscription<T> {
 
         private static final long serialVersionUID = -4896760517184205454L;
 
+        @Nullable
         @Override
         public T poll() {
             return queue.poll();
diff --git a/src/main/java/io/reactivex/subjects/UnicastSubject.java b/src/main/java/io/reactivex/subjects/UnicastSubject.java
index b6e0defdff..b5054d52ba 100644
--- a/src/main/java/io/reactivex/subjects/UnicastSubject.java
+++ b/src/main/java/io/reactivex/subjects/UnicastSubject.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.subjects;
 
+import io.reactivex.annotations.Nullable;
 import io.reactivex.plugins.RxJavaPlugins;
 import java.util.concurrent.atomic.*;
 
@@ -348,6 +349,7 @@ public int requestFusion(int mode) {
             return NONE;
         }
 
+        @Nullable
         @Override
         public T poll() throws Exception {
             return queue.poll();
diff --git a/src/test/java/io/reactivex/internal/observers/BasicFuseableObserverTest.java b/src/test/java/io/reactivex/internal/observers/BasicFuseableObserverTest.java
index ecde2fd062..93aef221b2 100644
--- a/src/test/java/io/reactivex/internal/observers/BasicFuseableObserverTest.java
+++ b/src/test/java/io/reactivex/internal/observers/BasicFuseableObserverTest.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.observers;
 
+import io.reactivex.annotations.Nullable;
 import org.junit.Test;
 
 import io.reactivex.disposables.Disposables;
@@ -24,6 +25,7 @@ public class BasicFuseableObserverTest {
     public void offer() {
         TestObserver<Integer> to = new TestObserver<Integer>();
         BasicFuseableObserver<Integer, Integer> o = new BasicFuseableObserver<Integer, Integer>(to) {
+            @Nullable
             @Override
             public Integer poll() throws Exception {
                 return null;
@@ -51,6 +53,7 @@ protected boolean beforeDownstream() {
     @Test(expected = UnsupportedOperationException.class)
     public void offer2() {
         BasicFuseableObserver<Integer, Integer> o = new BasicFuseableObserver<Integer, Integer>(new TestObserver<Integer>()) {
+            @Nullable
             @Override
             public Integer poll() throws Exception {
                 return null;
diff --git a/src/test/java/io/reactivex/internal/observers/BasicQueueDisposableTest.java b/src/test/java/io/reactivex/internal/observers/BasicQueueDisposableTest.java
index e10daebd1a..c98b080ae4 100644
--- a/src/test/java/io/reactivex/internal/observers/BasicQueueDisposableTest.java
+++ b/src/test/java/io/reactivex/internal/observers/BasicQueueDisposableTest.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.observers;
 
+import io.reactivex.annotations.Nullable;
 import org.junit.Test;
 
 public class BasicQueueDisposableTest {
@@ -29,6 +30,7 @@ public void dispose() {
 
         }
 
+        @Nullable
         @Override
         public Integer poll() throws Exception {
             return null;
diff --git a/src/test/java/io/reactivex/internal/operators/flowable/FlowableObserveOnTest.java b/src/test/java/io/reactivex/internal/operators/flowable/FlowableObserveOnTest.java
index 6c91db8217..5b61f110af 100644
--- a/src/test/java/io/reactivex/internal/operators/flowable/FlowableObserveOnTest.java
+++ b/src/test/java/io/reactivex/internal/operators/flowable/FlowableObserveOnTest.java
@@ -21,6 +21,7 @@
 import java.util.concurrent.*;
 import java.util.concurrent.atomic.*;
 
+import io.reactivex.annotations.Nullable;
 import org.junit.Test;
 import org.mockito.InOrder;
 import org.reactivestreams.*;
@@ -1363,6 +1364,7 @@ public boolean offer(Integer v1, Integer v2) {
                         return false;
                     }
 
+                    @Nullable
                     @Override
                     public Integer poll() throws Exception {
                         throw new TestException();
@@ -1413,6 +1415,7 @@ public boolean offer(Integer v1, Integer v2) {
                         return false;
                     }
 
+                    @Nullable
                     @Override
                     public Integer poll() throws Exception {
                         throw new TestException();
@@ -1464,6 +1467,7 @@ public boolean offer(Integer v1, Integer v2) {
                         return false;
                     }
 
+                    @Nullable
                     @Override
                     public Integer poll() throws Exception {
                         throw new TestException();
@@ -1514,6 +1518,7 @@ public boolean offer(Integer v1, Integer v2) {
                         return false;
                     }
 
+                    @Nullable
                     @Override
                     public Integer poll() throws Exception {
                         throw new TestException();
diff --git a/src/test/java/io/reactivex/internal/operators/observable/ObservableObserveOnTest.java b/src/test/java/io/reactivex/internal/operators/observable/ObservableObserveOnTest.java
index cd43e3f722..809bfe861f 100644
--- a/src/test/java/io/reactivex/internal/operators/observable/ObservableObserveOnTest.java
+++ b/src/test/java/io/reactivex/internal/operators/observable/ObservableObserveOnTest.java
@@ -21,6 +21,7 @@
 import java.util.concurrent.*;
 import java.util.concurrent.atomic.*;
 
+import io.reactivex.annotations.Nullable;
 import org.junit.Test;
 import org.mockito.InOrder;
 
@@ -692,6 +693,7 @@ public boolean offer(Integer v1, Integer v2) {
                         return false;
                     }
 
+                    @Nullable
                     @Override
                     public Integer poll() throws Exception {
                         throw new TestException();
diff --git a/src/test/java/io/reactivex/internal/subscribers/BasicFuseableConditionalSubscriberTest.java b/src/test/java/io/reactivex/internal/subscribers/BasicFuseableConditionalSubscriberTest.java
index b499462116..f3c98110b4 100644
--- a/src/test/java/io/reactivex/internal/subscribers/BasicFuseableConditionalSubscriberTest.java
+++ b/src/test/java/io/reactivex/internal/subscribers/BasicFuseableConditionalSubscriberTest.java
@@ -15,6 +15,7 @@
 
 import static org.junit.Assert.*;
 
+import io.reactivex.annotations.Nullable;
 import org.junit.Test;
 import org.reactivestreams.Subscription;
 
@@ -66,6 +67,7 @@ public int requestFusion(int mode) {
                 return 0;
             }
 
+            @Nullable
             @Override
             public Integer poll() throws Exception {
                 return null;
diff --git a/src/test/java/io/reactivex/internal/subscribers/BasicFuseableSubscriberTest.java b/src/test/java/io/reactivex/internal/subscribers/BasicFuseableSubscriberTest.java
index e1f9e685da..fb241bbb67 100644
--- a/src/test/java/io/reactivex/internal/subscribers/BasicFuseableSubscriberTest.java
+++ b/src/test/java/io/reactivex/internal/subscribers/BasicFuseableSubscriberTest.java
@@ -15,6 +15,7 @@
 
 import static org.junit.Assert.*;
 
+import io.reactivex.annotations.Nullable;
 import org.junit.Test;
 
 import io.reactivex.TestHelper;
@@ -36,6 +37,7 @@ public int requestFusion(int mode) {
                 return 0;
             }
 
+            @Nullable
             @Override
             public Integer poll() throws Exception {
                 return null;
diff --git a/src/test/java/io/reactivex/internal/subscriptions/QueueSubscriptionTest.java b/src/test/java/io/reactivex/internal/subscriptions/QueueSubscriptionTest.java
index 2a9e4c1f09..a098b99d44 100644
--- a/src/test/java/io/reactivex/internal/subscriptions/QueueSubscriptionTest.java
+++ b/src/test/java/io/reactivex/internal/subscriptions/QueueSubscriptionTest.java
@@ -13,6 +13,7 @@
 
 package io.reactivex.internal.subscriptions;
 
+import io.reactivex.annotations.Nullable;
 import org.junit.Test;
 
 import static org.junit.Assert.*;
@@ -28,6 +29,7 @@ public int requestFusion(int mode) {
             return 0;
         }
 
+        @Nullable
         @Override
         public Integer poll() throws Exception {
             return null;
@@ -64,6 +66,7 @@ public int requestFusion(int mode) {
             return 0;
         }
 
+        @Nullable
         @Override
         public Integer poll() throws Exception {
             return null;