diff --git a/core/src/com/google/inject/Module.java b/core/src/com/google/inject/Module.java
index 52cdd30689..ac9d7c68ae 100644
--- a/core/src/com/google/inject/Module.java
+++ b/core/src/com/google/inject/Module.java
@@ -28,6 +28,7 @@
  * all methods annotated with {@literal @}{@link Provides}. Use scope and binding annotations on
  * these methods to configure the bindings.
  */
+@FunctionalInterface
 public interface Module {
 
   /**