diff --git a/src/java/org/apache/cassandra/net/MessagingService.java b/src/java/org/apache/cassandra/net/MessagingService.java
index <HASH>..<HASH> 100644
--- a/src/java/org/apache/cassandra/net/MessagingService.java
+++ b/src/java/org/apache/cassandra/net/MessagingService.java
@@ -548,7 +548,7 @@ public final class MessagingService implements MessagingServiceMBean
 
     public int addCallback(IAsyncCallback cb, MessageOut<? extends IMutation> message, InetAddress to, long timeout, ConsistencyLevel consistencyLevel)
     {
-        assert message.verb == Verb.MUTATION;
+        assert message.verb == Verb.MUTATION || message.verb == Verb.COUNTER_MUTATION;
         int messageId = nextId();
         CallbackInfo previous = callbacks.put(messageId, new WriteCallbackInfo(to, cb, message, callbackDeserializers.get(message.verb), consistencyLevel), timeout);
         assert previous == null;
fix assert for counters (CASSANDRA-<I>)