diff --git a/src/main/java/org/jboss/netty/handler/codec/http/websocketx/WebSocketClientHandshaker.java b/src/main/java/org/jboss/netty/handler/codec/http/websocketx/WebSocketClientHandshaker.java
index b23af2a9b7..74bb317832 100644
--- a/src/main/java/org/jboss/netty/handler/codec/http/websocketx/WebSocketClientHandshaker.java
+++ b/src/main/java/org/jboss/netty/handler/codec/http/websocketx/WebSocketClientHandshaker.java
@@ -35,7 +35,7 @@ public abstract class WebSocketClientHandshaker {
 
     private final String expectedSubprotocol;
 
-    private String actualSubprotocol;
+    private volatile String actualSubprotocol;
 
     protected final Map<String, String> customHeaders;