Reference attribute retaining old value in metaverse

I have a reference attribute called "teamLeader" in the Metaverse, which is being imported from the FIM management agent and no other flow.

If the value in FIM is null, the previous value in the metaverse is not cleared:

If I check the MV object, I see that the value is contributed by FIM:

However, if I check the FIM MA connector space, I don't see the attribute at all (since it's null).

The only import flow defined is from the FIM MA, and it's a simple direct flow.

Is there any way I can force a cleanup of this attribute?

Thanks,
Paolo

Paolo Tedesco - http://cern.ch/idm