Inserting a simple fact (just String instance) via REST /runtime/

/execute ended with an exception:
Unable to add result from InsertObjectCommand because of UnsupportedOperationException: java.lang.UnsupportedOperationException: Result type DefaultFactHandle from command InsertObjectCommand is an unsupported response type.

It seems that the command itself can be processed, but the result - DefaultFactHandle cannot be serialized in JaxbCommandsResponse class.

Attaching full stacktrace.

version: community 6.0.0.CR1