diff --git a/supplier/spring-twitter-supplier/src/main/java/org/springframework/cloud/fn/supplier/twitter/message/TwitterMessageSupplierConfiguration.java b/supplier/spring-twitter-supplier/src/main/java/org/springframework/cloud/fn/supplier/twitter/message/TwitterMessageSupplierConfiguration.java
index 66035ad1..a8363db4 100644
--- a/supplier/spring-twitter-supplier/src/main/java/org/springframework/cloud/fn/supplier/twitter/message/TwitterMessageSupplierConfiguration.java
+++ b/supplier/spring-twitter-supplier/src/main/java/org/springframework/cloud/fn/supplier/twitter/message/TwitterMessageSupplierConfiguration.java
@@ -143,7 +143,7 @@ public class TwitterMessageSupplierConfiguration {
 	}
 
 	@SuppressWarnings("serial")
-	private static class DirectMessageAdapter implements DirectMessage {
+	private static final class DirectMessageAdapter implements DirectMessage {
 
 		private final DirectMessage delegate;