diff --git a/src/main/java/com/hubspot/jinjava/interpret/JinjavaInterpreter.java b/src/main/java/com/hubspot/jinjava/interpret/JinjavaInterpreter.java
index 8e0510aca..a85b756b1 100644
--- a/src/main/java/com/hubspot/jinjava/interpret/JinjavaInterpreter.java
+++ b/src/main/java/com/hubspot/jinjava/interpret/JinjavaInterpreter.java
@@ -78,6 +78,9 @@ public class JinjavaInterpreter implements PyishSerializable {
 
   public static final String IGNORED_OUTPUT_FROM_EXTENDS_NOTE =
     "ignored_output_from_extends";
+
+  public static final String OUTPUT_UNDEFINED_VARIABLES_ERROR =
+    "OUTPUT_UNDEFINED_VARIABLES_ERROR";
   private final Multimap<String, BlockInfo> blocks = ArrayListMultimap.create();
   private final LinkedList<Node> extendParentRoots = new LinkedList<>();
   private final Map<String, RevertibleObject> revertibleObjects = new HashMap<>();
@@ -585,6 +588,28 @@ public Object retraceVariable(String variable, int lineNumber, int startPosition
         }
       }
       obj = var.resolve(obj);
+    } else {
+      if (
+        getConfig()
+          .getFeatures()
+          .getActivationStrategy(OUTPUT_UNDEFINED_VARIABLES_ERROR)
+          .isActive(context)
+      ) {
+        addError(
+          new TemplateError(
+            ErrorType.WARNING,
+            ErrorReason.UNKNOWN,
+            ErrorItem.TOKEN,
+            "Undefined variable: '" + variable + "'",
+            null,
+            lineNumber,
+            startPosition,
+            null,
+            BasicTemplateErrorCategory.UNKNOWN,
+            ImmutableMap.of("variable", variable)
+          )
+        );
+      }
     }
     return obj;
   }
diff --git a/src/test/java/com/hubspot/jinjava/interpret/JinjavaInterpreterTest.java b/src/test/java/com/hubspot/jinjava/interpret/JinjavaInterpreterTest.java
index e8e9641a1..f866db349 100644
--- a/src/test/java/com/hubspot/jinjava/interpret/JinjavaInterpreterTest.java
+++ b/src/test/java/com/hubspot/jinjava/interpret/JinjavaInterpreterTest.java
@@ -557,4 +557,47 @@ public void itPreventsAccidentalExpressions() {
       JinjavaInterpreter.popCurrent();
     }
   }
+
+  @Test
+  public void itOutputsUndefinedVariableError() {
+    String template = "{% set foo=123 %}{{ foo }}{{ bar }}";
+
+    JinjavaInterpreter normalInterpreter = new JinjavaInterpreter(
+      jinjava,
+      jinjava.getGlobalContext(),
+      JinjavaConfig.newBuilder().withExecutionMode(EagerExecutionMode.instance()).build()
+    );
+    JinjavaInterpreter outputtingErrorInterpreters = new JinjavaInterpreter(
+      jinjava,
+      jinjava.getGlobalContext(),
+      JinjavaConfig
+        .newBuilder()
+        .withFeatureConfig(
+          FeatureConfig
+            .newBuilder()
+            .add(
+              JinjavaInterpreter.OUTPUT_UNDEFINED_VARIABLES_ERROR,
+              FeatureStrategies.ACTIVE
+            )
+            .build()
+        )
+        .withExecutionMode(EagerExecutionMode.instance())
+        .build()
+    );
+
+    String normalRenderResult = normalInterpreter.render(template);
+    String outputtingErrorRenderResult = outputtingErrorInterpreters.render(template);
+    assertThat(normalRenderResult).isEqualTo("123");
+    assertThat(outputtingErrorRenderResult).isEqualTo("123");
+    assertThat(normalInterpreter.getErrors()).isEmpty();
+    assertThat(outputtingErrorInterpreters.getErrors().size()).isEqualTo(1);
+    assertThat(outputtingErrorInterpreters.getErrors().get(0).getMessage())
+      .contains("Undefined variable: 'bar'");
+    assertThat(outputtingErrorInterpreters.getErrors().get(0).getReason())
+      .isEqualTo(ErrorReason.UNKNOWN);
+    assertThat(outputtingErrorInterpreters.getErrors().get(0).getSeverity())
+      .isEqualTo(ErrorType.WARNING);
+    assertThat(outputtingErrorInterpreters.getErrors().get(0).getCategoryErrors())
+      .isEqualTo(ImmutableMap.of("variable", "bar"));
+  }
 }