diff --git a/services/univention-ldb-modules/modules/univention_samaccountname_ldap_check.c b/services/univention-ldb-modules/modules/univention_samaccountname_ldap_check.c
index 209a1e5..f1c66c5 100644
--- a/services/univention-ldb-modules/modules/univention_samaccountname_ldap_check.c
+++ b/services/univention-ldb-modules/modules/univention_samaccountname_ldap_check.c
@@ -282,15 +282,15 @@ static int univention_samaccountname_ldap_check_add(struct ldb_module *module, s
 		if( ! WIFEXITED(status) ) {
 			ldb_debug(ldb, LDB_DEBUG_ERROR, "%s: Cannot determine return status of ucs-school-create_windows_computer: %s (%d)\n", ldb_module_get_name(module), strerror(errno_wait), errno_wait);
 			return LDB_ERR_UNWILLING_TO_PERFORM;
-		} else if( WEXITSTATUS(status) == 1 ) {
-			ldb_debug(ldb, LDB_DEBUG_ERROR, "%s: LDB_ERR_ENTRY_ALREADY_EXISTS\n", ldb_module_get_name(module));
-			return LDB_ERR_ENTRY_ALREADY_EXISTS;
 		} else if( WEXITSTATUS(status) == 2 ) {
 			ldb_debug(ldb, LDB_DEBUG_ERROR, ("%s: ldb_add of machine object is disabled\n"), ldb_module_get_name(module));
 			return LDB_ERR_UNWILLING_TO_PERFORM;
 		} else if( WEXITSTATUS(status) == 3 ) {
 			ldb_debug(ldb, LDB_DEBUG_TRACE, ("%s: ldb_add of machine object ignored in dummy mode\n"), ldb_module_get_name(module));
 			return LDB_SUCCESS;
+		} else if( WEXITSTATUS(status) == 4 ) {
+			ldb_debug(ldb, LDB_DEBUG_ERROR, "%s: LDB_ERR_ENTRY_ALREADY_EXISTS\n", ldb_module_get_name(module));
+			return LDB_ERR_ENTRY_ALREADY_EXISTS;
 		} else if( WEXITSTATUS(status) ) {
 			ldb_debug(ldb, LDB_DEBUG_ERROR, ("%s: unknown error code from ucs-school-create_windows_computer: %d\n"), ldb_module_get_name(module), WEXITSTATUS(status));
 			return LDB_ERR_UNWILLING_TO_PERFORM;
diff --git a/services/univention-ldb-modules/ucs-school-create_windows_computer b/services/univention-ldb-modules/ucs-school-create_windows_computer
index 8bbce98..db058d8 100755
--- a/services/univention-ldb-modules/ucs-school-create_windows_computer
+++ b/services/univention-ldb-modules/ucs-school-create_windows_computer
@@ -61,6 +61,7 @@ def main():
 	options['school'] = SchoolSearchBase.getOU(ucr.get('ldap/hostdn', '')) or SchoolSearchBase.getOU(ucr.get('dhcpd/ldap/base', ''))
 	client = Client(args.server, args.username, args.password)
 	result = client.umc_command(args.command, options).result
+	existed = result.get('existed')
 	dn_ol = result.get('dn')
 	if not dn_ol:
 		# sys.exit(1)
@@ -71,6 +72,8 @@ def main():
 
 	dn_s4 = dn_ol[:len(dn_ol) - len(ldap_base)] + samba4_ldap_base
 	print dn_s4
+	if existed:
+		sys.exit(4)
 
 
 if __name__ == '__main__':
diff --git a/univention-management-console-module-selective-udm/umc/python/selective-udm/__init__.py b/univention-management-console-module-selective-udm/umc/python/selective-udm/__init__.py
index d92500e..cdf928d 100644
--- a/univention-management-console-module-selective-udm/umc/python/selective-udm/__init__.py
+++ b/univention-management-console-module-selective-udm/umc/python/selective-udm/__init__.py
@@ -40,6 +40,7 @@
 import univention.admin.modules
 import univention.admin.objects
 import univention.admin.uldap
+import univention.admin.uexceptions
 import univention.admin.handlers.users.user
 import univention.admin.handlers.computers.windows
 
@@ -121,5 +122,10 @@ def create_windows_computer(self, request, ldap_user_read=None, ldap_admin_write
 			computer['password'] = password
 
 		computer['description'] = request.options.get('description')
-		computer_dn = computer.create()
-		self.finished(request.id, {'dn': computer_dn})
+		try:
+			computer_dn = computer.create()
+			existed = False
+		except univention.admin.uexceptions.objectExists as exc:
+			existed = True
+			computer_dn = exc.args[0]
+		self.finished(request.id, {'dn': computer_dn, 'existed': existed})