<hr /><i>oehhar added on 2018-01-15 15:04:49 UTC:</i><br />
Thank you for the ticket!

Gerald wrote by private mail about it:

The code to handle incoming abstract types seems to be missing -- the outgoing code is there.

There should have been code in the Convert Type to Dictionary code that looks to see if the ::type attribute exists, and use that type instead of the "expected" type.