Wall assisted shoulder opening

Believe it or not, but it took me more than a year to get this "move" (steve atlas is demonstrating the move in the video below) down. I had terrible shoulder flexibility.  Today was the first day I could do this, and I have a question.

 

 

When I push my chest away from the wall to get my butt on the wall I notice that my shoulder start to internally rotate. I can hold the position and even relax, but is this correct? If I try to prevent my shoulder from internally rotating, then the move/stretch is impossible for me.

 

Any suggestions? 

It's normal to externally rotate, I would focus on pushing the chest forward. Also pair this exercise up with stomach facing wall shrugs and focus on elevating your shoulders as much as possible.