diff --git a/core/src/test/scala/de/commercetools/queue/testing/LockedTestMessage.scala b/core/src/test/scala/de/commercetools/queue/testing/LockedTestMessage.scala
index c99197a..db17de1 100644
--- a/core/src/test/scala/de/commercetools/queue/testing/LockedTestMessage.scala
+++ b/core/src/test/scala/de/commercetools/queue/testing/LockedTestMessage.scala
@@ -51,4 +51,8 @@ final case class LockedTestMessage[T](
       }
     }
 
+  /**
+   * Unique message identifier
+   */
+  override val messageId: String = lock.toString
 }