Comments webhook is not triggered when a Gitlab issue is mentioned in the commit discussion

Version : Gitlab CE 9.1.0
Create a webhook and add set the comments trigger.

Push a new commit.
Open and view the commit in a web browser.
Add some comment which does not comtain any Gitlab issue. Webhook is triggered.
Add another comment which contains a gitlab issue eg : “look at #2” Webhook is not triggered.