# UNDF: UNDF-2026-000000132
--- a/keystone/api/users.py
+++ b/keystone/api/users.py
@@ -663,7 +663,7 @@ class UsersResource(ks_flask.ResourceBase):
             # credential users from escallating their privileges to include
             # additional roles that the trustor or application credential
             # creator has assigned on the project.
-            token_roles = [r['id'] for r in token.roles]
+            token_role_ids = {r['id'] for r in token.roles}
             for role in roles:
-                if role['id'] not in token_roles:
+                if role['id'] not in token_role_ids:
                     detail = _(
                         'Cannot create an application credential with '
                         'unassigned role'