Search for users in sharing tab (LDAP related)

So we have pas.plugins.ldap 1.5.3 (plone 5.0.8), in the sharing tab we can add users by "firstname lastname" or "id" but not just lastname. I remember in the old days if we searched for lastname all people with the same lastname would be added to the list, but not now. It just doesn't show anything. No errors, nothing.
The settings for ldap hasn't changed and it communicates with AD ok.
Is this a bug or a feature or is there a setting somewhere that lets me do that?