diff --git a/src/core.cpp b/src/core.cpp
index 93d2cb59..21f07582 100644
--- a/src/core.cpp
+++ b/src/core.cpp
@@ -84,7 +84,7 @@ uint256 CTransaction::GetUsernameHash() const
         return SerializeHash(userName.ExtractSmallString());
     }
     // [MF] TODO: remove this assert later, it will fail for spammessage.
-    assert(!"username not small string");
+    //assert(!"username not small string");
     return uint256();
 }
 
diff --git a/src/main.cpp b/src/main.cpp
index ad48664c..e72e38d7 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -494,6 +494,8 @@ bool CheckTransaction(const CTransaction& tx, CValidationState &state)
           return state.DoS(10, error("CheckTransaction() : pubKey empty"));
       if (!tx.userName.IsSmallString())
           return state.DoS(10, error("CheckTransaction() : username not smallstring"));
+      if (tx.GetUsernameHash() == uint256())
+          return state.DoS(10, error("CheckTransaction() : username hash error"));
       if (!CheckUsername( tx.userName.ExtractSmallString(), state ))
           return state.DoS(10, error("CheckTransaction() : username check failed"));
     }