diff --git a/core/src/main/java/org/springframework/security/authentication/AuthenticationManager.java b/core/src/main/java/org/springframework/security/authentication/AuthenticationManager.java
index b98c8351497..b95d8c4f078 100644
--- a/core/src/main/java/org/springframework/security/authentication/AuthenticationManager.java
+++ b/core/src/main/java/org/springframework/security/authentication/AuthenticationManager.java
@@ -23,7 +23,9 @@
  * Processes an {@link Authentication} request.
  *
  * @author Ben Alex
+ * @author KyeongHoon Lee
  */
+@FunctionalInterface
 public interface AuthenticationManager {
 
 	/**