Airleak at top of mirror housing and window

[Coaster]

I have one annoying air leak on the driver side right where the top of the mirror housing and the glass meet. I can push on the top of the triangle with my finger to make it go away. Do I have to replace the door gasket to fix it or can I adjust the window up? I don't drive with the top down all the time and don't want to hold my finger there all the time either