REST API /solutions/solution/unmark ?

Hi,

There is an API call to mark a message as a solution :

http://community.lithium.com/community-name/restapi/vc/messages/id/1271/solutions/solution/mark

Naturally I was wondering if there is any API call to unmark a message but in 12.7 doesn't say anything.

I tried without success :  

http://community.lithium.com/community-name/restapi/vc/messages/id/1271/solutions/solution/unmark