diff --git a/tempest/common/credentials_factory.py b/tempest/common/credentials_factory.py
index 58157ef..3923aec 100644
--- a/tempest/common/credentials_factory.py
+++ b/tempest/common/credentials_factory.py
@@ -133,7 +133,7 @@
     def get_creds_by_roles(self, roles, force_new=False):
         msg = "Credentials being specified through the config file can not be"\
               " used with tests that specify using credentials by roles. "\
-              "Either exclude/skip the tests doing this or use either an "\
+              "Either exclude/skip the tests doing this or use either a "\
               "test_accounts_file or dynamic credentials."
         raise exceptions.InvalidConfiguration(msg)