diff --git a/rmw_cyclonedds_cpp/src/rmw_node.cpp b/rmw_cyclonedds_cpp/src/rmw_node.cpp
index d9d70830..1339c4ec 100644
--- a/rmw_cyclonedds_cpp/src/rmw_node.cpp
+++ b/rmw_cyclonedds_cpp/src/rmw_node.cpp
@@ -1380,7 +1380,7 @@ extern "C" rmw_ret_t rmw_get_serialized_message_size(
   static_cast<void>(size);
 
   RMW_SET_ERROR_MSG("rmw_get_serialized_message_size: unimplemented");
-  return RMW_RET_ERROR;
+  return RMW_RET_UNSUPPORTED;
 }
 
 extern "C" rmw_ret_t rmw_serialize(