diff --git a/services/univention-s4-connector/modules/univention/s4connector/s4/__init__.py b/services/univention-s4-connector/modules/univention/s4connector/s4/__init__.py
index 6d5fb6c4d2..aa3f8d155f 100644
--- a/services/univention-s4-connector/modules/univention/s4connector/s4/__init__.py
+++ b/services/univention-s4-connector/modules/univention/s4connector/s4/__init__.py
@@ -353,12 +353,14 @@ def samaccountname_dn_mapping(s4connector, given_object, dn_mapping_stored, ucso
 						newdn = unicode(result[0][0], 'utf8')
 					else:
 						s4_rdn = ldap.dn.str2dn(result[0][0])[0]
-						new_s4_dn = unicode(ldap.dn.dn2str([s4_rdn] + exploded_dn[1:]), 'utf8')
-						pos = new_s4_dn.lower().rfind(s4connector.lo_s4.base.lower())
-						newdn = new_s4_dn[:pos] + s4connector.lo.base
+						tmp_dn_string = unicode(ldap.dn.dn2str([s4_rdn] + exploded_dn[1:]), 'utf8')
+						pos = tmp_dn_string.lower().rfind(s4connector.lo.base.lower())
+						newdn = tmp_dn_string[:pos] + s4connector.lo_s4.base
 				else:
 					newdn_rdn = [('cn', fst_rdn_value_utf8, ldap.AVA_STRING)]
-					newdn = unicode(ldap.dn.dn2str([newdn_rdn] + exploded_dn[1:]), 'utf8')  # new object, don't need to change
+					tmp_dn_string = unicode(ldap.dn.dn2str([newdn_rdn] + exploded_dn[1:]), 'utf8')  # new object, don't need to change
+					pos = tmp_dn_string.lower().rfind(s4connector.lo.base.lower())
+					newdn = tmp_dn_string[:pos] + s4connector.lo_s4.base
 				ud.debug(ud.LDAP, ud.INFO, "samaccount_dn_mapping: newdn: %s" % newdn)
 			else:
 				# get the object to read the sAMAccountName in S4 and use it as name
@@ -408,7 +410,9 @@ def samaccountname_dn_mapping(s4connector, given_object, dn_mapping_stored, ucso
 					else:
 						newdn_rdn = [(ucsattrib, unicode_to_utf8(samaccountname), ldap.AVA_STRING)]
 
-					newdn = unicode(ldap.dn.dn2str([newdn_rdn] + exploded_dn[1:]), 'utf8')  # guess the old dn
+					tmp_dn_string = unicode(ldap.dn.dn2str([newdn_rdn] + exploded_dn[1:]), 'utf8')  # guess the old dn
+					pos = tmp_dn_string.lower().rfind(s4connector.lo_s4.base.lower())
+					newdn = tmp_dn_string[:pos] + s4connector.lo.base
 			try:
 				ud.debug(ud.LDAP, ud.INFO, "samaccount_dn_mapping: newdn for key %s:" % dn_key)
 				ud.debug(ud.LDAP, ud.INFO, "samaccount_dn_mapping: olddn: %s" % dn)