diff --git a/appengine/flexible/endpoints/openapi.yaml b/appengine/flexible/endpoints/openapi.yaml
index e65030a4e5f7..d0ad93eeb706 100644
--- a/appengine/flexible/endpoints/openapi.yaml
+++ b/appengine/flexible/endpoints/openapi.yaml
@@ -104,12 +104,14 @@ definitions:
       email:
         type: "string"
 
+# [START securityDef]
 securityDefinitions:
   # This section configures basic authentication with an API key.
   api_key:
     type: "apiKey"
     name: "key"
     in: "query"
+# [END securityDef]
   # This section configures authentication using Google API Service Accounts
   # to sign a json web token. This is mostly used for server-to-server
   # communication.