diff --git a/src/net45/WampSharp/WAMP2/V2/PubSub/WampRawTopic.cs b/src/net45/WampSharp/WAMP2/V2/PubSub/WampRawTopic.cs
index 7c2a39e43..597ed7f06 100644
--- a/src/net45/WampSharp/WAMP2/V2/PubSub/WampRawTopic.cs
+++ b/src/net45/WampSharp/WAMP2/V2/PubSub/WampRawTopic.cs
@@ -199,8 +199,11 @@ public void Unsubscribe(IUnsubscribeRequest<TMessage> request)
 
         public void Dispose()
         {
-            SubscriptionDisposable.Dispose();
-            SubscriptionDisposable = null;
+            if (SubscriptionDisposable != null)
+            {
+                SubscriptionDisposable.Dispose();
+                SubscriptionDisposable = null;
+            }
         }
 
         #endregion