diff --git a/source/Runtime/Common/MessageProcessor.cs b/source/Runtime/Common/MessageProcessor.cs
index 6e7043f..95b7c58 100644
--- a/source/Runtime/Common/MessageProcessor.cs
+++ b/source/Runtime/Common/MessageProcessor.cs
@@ -166,7 +166,7 @@ static void ThrowIfBadOpCode(int opcode, bool finished, bool opCodeContinuation)
                 if (opcode == 2 || opcode == 8)
                     return;
 
-                throw new InvalidDataException("Expected opcode to be binary or close");
+                throw new InvalidDataException($"Unexpected opcode {opcode}");
             }
         }