Permissions for Organic Group mapping

I am using a feed within OG where I map OG in "Mapping for Node Processor".

It all works. Feed-Items appear in the same group as where the Feed is created, except for one thing.
My groups are all "private groups", but the Feed-Items are visible for everyone.
It seems that creating the Feed-Items does not take the Access Control functionality of OG into consideration.

When I edit a created Feed-Item and save it again without any change, it does have the right Access Control permissions.