diff --git a/demo/openapi.yaml b/demo/openapi.yaml
index 0adb6933..8cecfd5a 100644
--- a/demo/openapi.yaml
+++ b/demo/openapi.yaml
@@ -910,6 +910,7 @@ components:
         message:
           type: string
     Cat:
+      'x-tags': ['pet']
       description: A representation of a cat
       allOf:
         - $ref: '#/components/schemas/Pet'