[Zope] "Undo changes" strange behaviour of permission propagation

Hi there, This is with Zope 2.62 I want to offer Plones "Quick undo" to a user only in some parts of a site. When I test for the right whether he is allowed to "Undo chages" with the following test that checks what roles are allowed a permission [ s for s in map(lambda x : len(x['selected']) and x['name'], context.rolesOfPermission('Undo changes')) if s] I do not get the inherited roles but only the ones assigned to the folder I perform the test on. If I do the same for "View" I get also the inherited permissions. Should not rolesOfPermission also return the inherited roles ? Robert