diff --git a/kallithea/controllers/api/api.py b/kallithea/controllers/api/api.py
--- a/kallithea/controllers/api/api.py
+++ b/kallithea/controllers/api/api.py
@@ -1160,7 +1160,7 @@ class ApiController(JSONRPCController):
             return _map[ret_type]
         except KeyError:
             raise JSONRPCError('ret_type must be one of %s'
-                               % (','.join(_map.keys())))
+                               % (','.join(sorted(_map))))
         except Exception:
             log.error(traceback.format_exc())
             raise JSONRPCError(
diff --git a/kallithea/tests/api/api_base.py b/kallithea/tests/api/api_base.py
--- a/kallithea/tests/api/api_base.py
+++ b/kallithea/tests/api/api_base.py
@@ -807,7 +807,7 @@ class _BaseTestApi(object):
         response = api_call(self, params)
 
         expected = ('ret_type must be one of %s'
-                    % (','.join(['files', 'dirs', 'all'])))
+                    % (','.join(sorted(['files', 'dirs', 'all']))))
         self._compare_error(id_, expected, given=response.body)
 
     @parametrize('name,ret_type,grant_perm', [