diff --git a/faiss/utils/Heap.cpp b/faiss/utils/Heap.cpp
index 63981ba6dc..16ee23f6c8 100644
--- a/faiss/utils/Heap.cpp
+++ b/faiss/utils/Heap.cpp
@@ -93,7 +93,7 @@ void HeapArray<C>::addn_query_subset_with_ids(
     }
 #pragma omp parallel for if (nsubset * nj > 100000)
     for (int64_t si = 0; si < nsubset; si++) {
-        T i = subset[si];
+        TI i = subset[si];
         T* __restrict simi = get_val(i);
         TI* __restrict idxi = get_ids(i);
         const T* ip_line = vin + si * nj;
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index dfe8c13394..8167c7dfc7 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -26,6 +26,7 @@ set(FAISS_TEST_SRC
   test_approx_topk.cpp
   test_RCQ_cropping.cpp
   test_distances_simd.cpp
+  test_heap.cpp
 )
 
 add_executable(faiss_test ${FAISS_TEST_SRC})
diff --git a/tests/test_heap.cpp b/tests/test_heap.cpp
new file mode 100644
index 0000000000..9481003db6
--- /dev/null
+++ b/tests/test_heap.cpp
@@ -0,0 +1,53 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+#include <faiss/utils/Heap.h>
+#include <gtest/gtest.h>
+#include <algorithm>
+#include <numeric>
+
+using namespace faiss;
+
+TEST(Heap, addn_with_ids) {
+    size_t n = 1000;
+    size_t k = 1;
+    std::vector<int64_t> heap_labels(n, -1);
+    std::vector<float> heap_distances(n, 0);
+    float_minheap_array_t heaps = {
+            n, k, heap_labels.data(), heap_distances.data()};
+    heaps.heapify();
+    std::vector<int64_t> labels(n, 1);
+    std::vector<float> distances(n, 0.0f);
+    std::vector<int64_t> subset(n);
+    std::iota(subset.begin(), subset.end(), 0);
+    heaps.addn_with_ids(1, distances.data(), labels.data(), 1);
+    heaps.reorder();
+    EXPECT_TRUE(
+            std::all_of(heap_labels.begin(), heap_labels.end(), [](int64_t i) {
+                return i == 1;
+            }));
+}
+
+TEST(Heap, addn_query_subset_with_ids) {
+    size_t n = 20000000; // more than 2^24
+    size_t k = 1;
+    std::vector<int64_t> heap_labels(n, -1);
+    std::vector<float> heap_distances(n, 0);
+    float_minheap_array_t heaps = {
+            n, k, heap_labels.data(), heap_distances.data()};
+    heaps.heapify();
+    std::vector<int64_t> labels(n, 1);
+    std::vector<float> distances(n, 0.0f);
+    std::vector<int64_t> subset(n);
+    std::iota(subset.begin(), subset.end(), 0);
+    heaps.addn_query_subset_with_ids(
+            n, subset.data(), 1, distances.data(), labels.data(), 1);
+    heaps.reorder();
+    EXPECT_TRUE(
+            std::all_of(heap_labels.begin(), heap_labels.end(), [](int64_t i) {
+                return i == 1;
+            }));
+}