Discussion from Closed group appears in 'public' stream

Hi there

I have created a closed group and started a discussion in this group, but I've noticed that discussion started within the closed group are not limited in their visibility to group members and posts are appearing in the general community feed.

Is this 'standard functionality' or do i have something configured incorrectly to have this work as I would expect - only members of a closed group should be able to view and respond to closed group discussions.