diff --git a/src/java.base/share/classes/java/lang/StringBuffer.java b/src/java.base/share/classes/java/lang/StringBuffer.java
index 959dd01fe5c..ec7ecb5d245 100644
--- a/src/java.base/share/classes/java/lang/StringBuffer.java
+++ b/src/java.base/share/classes/java/lang/StringBuffer.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1994, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -111,7 +111,7 @@ import jdk.internal.vm.annotation.IntrinsicCandidate;
  */
  public final class StringBuffer
     extends AbstractStringBuilder
-    implements Serializable, Comparable<StringBuffer>, CharSequence
+    implements Appendable, Serializable, Comparable<StringBuffer>, CharSequence
 {
 
     /**
diff --git a/src/java.base/share/classes/java/lang/StringBuilder.java b/src/java.base/share/classes/java/lang/StringBuilder.java
index add50081c77..c42422e6277 100644
--- a/src/java.base/share/classes/java/lang/StringBuilder.java
+++ b/src/java.base/share/classes/java/lang/StringBuilder.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -90,7 +90,7 @@ import java.io.StreamCorruptedException;
  */
 public final class StringBuilder
     extends AbstractStringBuilder
-    implements java.io.Serializable, Comparable<StringBuilder>, CharSequence
+    implements Appendable, java.io.Serializable, Comparable<StringBuilder>, CharSequence
 {
 
     /** use serialVersionUID for interoperability */