diff --git a/ldapuserdir/ldapuserdir.py b/ldapuserdir/ldapuserdir.py
index fb0a8ee..93ddd47 100755
--- a/ldapuserdir/ldapuserdir.py
+++ b/ldapuserdir/ldapuserdir.py
@@ -649,18 +649,20 @@ class LdapUserDir(object):
                     for submember in self._get_all_members(cn, include_groups=include_groups, ou=ou, mssfu=mssfu):
                         yield submember
 
-    @staticmethod
-    def _is_group(dn):
-        """Quick check if a DN is a group. That is, if it contains OU=Groups.
-
-        This may be a PSI-specific check
+    def _is_group(self, dn):
+        """Quick check if a DN is a group.
 
         Parameters
         ----------
         dn : str
            DN of the entry
         """
-        return "OU=Groups" in dn
+        
+        # self.logger.debug("_is_group: %s %s:" % (self.group_ou, dn))
+
+        # Note that lower() is not a good casefold alternative
+        # but this is python 2
+        return self.group_ou.lower() in dn.lower()
 
     def _mod_groupmembers(self, ldapmode, dngroup, usernames):
         """modifies (adds/deletes) members of an LDAP group entry