diff --git a/utils/netty/src/main/java/org/onlab/netty/InternalMessage.java b/utils/netty/src/main/java/org/onlab/netty/InternalMessage.java
index 96cbe79..109322d 100644
--- a/utils/netty/src/main/java/org/onlab/netty/InternalMessage.java
+++ b/utils/netty/src/main/java/org/onlab/netty/InternalMessage.java
@@ -55,7 +55,7 @@
     /**
      * Builder for InternalMessages.
      */
-    public static class Builder {
+    public static final class Builder {
         private InternalMessage message;
 
         public Builder(NettyMessagingService messagingService) {