diff --git a/spring-core/src/main/java/org/springframework/cglib/core/Transformer.java b/spring-core/src/main/java/org/springframework/cglib/core/Transformer.java
index cdbfef8473b4..76c38ad83219 100644
--- a/spring-core/src/main/java/org/springframework/cglib/core/Transformer.java
+++ b/spring-core/src/main/java/org/springframework/cglib/core/Transformer.java
@@ -15,6 +15,7 @@
  */
 package org.springframework.cglib.core;
 
+@FunctionalInterface
 public interface Transformer {
     Object transform(Object value);
 }