diff --git a/src/main/java/org/java_websocket/drafts/Draft_6455.java b/src/main/java/org/java_websocket/drafts/Draft_6455.java
index eb4879976..a91a75dea 100644
--- a/src/main/java/org/java_websocket/drafts/Draft_6455.java
+++ b/src/main/java/org/java_websocket/drafts/Draft_6455.java
@@ -244,7 +244,7 @@ public Draft_6455(List<IExtension> inputExtensions, List<IProtocol> inputProtoco
     boolean hasDefault = false;
     byteBufferList = new ArrayList<>();
     for (IExtension inputExtension : inputExtensions) {
-      if (inputExtension.getClass().equals(DefaultExtension.class)) {
+      if (inputExtension instanceof DefaultExtension) {
         hasDefault = true;
       }
     }