!important does not override Style

[lauritowal]

I am trying to override the height of the thumbnail using mixins with height: auto !important; :
--google-youtube-thumbnail: { height: auto !important; // using !important does not override }; }
As you can see in the following example: https://jsbin.com/dudepucini/edit?html,console,output
By inspecting the thumbnail on the right with the dev tools, height: auto is not applied to the thumbnail img.