diff --git a/spring-context/src/main/java/org/springframework/cache/interceptor/SimpleKey.java b/spring-context/src/main/java/org/springframework/cache/interceptor/SimpleKey.java
index cc3b0e59048..805edbbaadc 100644
--- a/spring-context/src/main/java/org/springframework/cache/interceptor/SimpleKey.java
+++ b/spring-context/src/main/java/org/springframework/cache/interceptor/SimpleKey.java
@@ -26,6 +26,7 @@ import org.springframework.util.StringUtils;
  * A simple key as returned from the {@link SimpleKeyGenerator}.
  *
  * @author Phillip Webb
+ * @since 4.0
  * @see SimpleKeyGenerator
  */
 public final class SimpleKey implements Serializable {