Scaling proportionally on After Effects - Shift + click does not work! For the life of me, I can't tell what I'm doing wrong, but here we are!

I am on Mac, newbie on After Effects. I can scale anything (not proportionally) with the click on a corner but, unlike in Indesign or Illustrator, Shift + click just does not work! It kind of releases the frame, just like if I had clicked outside of it. 

I am on Mac, After Effects CC. I verified the following:


Shift is pushed (the "non permanent capital letter" key of the keyboard)
Mode is "Selection tool" (the arrow)
I am indeed clicking on a corner (where little square appears) and not on the side!


Yet it just deselects the whole thing and making me crazy! What am I missing?
When I hold down shift, images and shapes scale proportionally. Just grab a corner handle and drag. 

Alternatively:
Select the layer, press S to reveal the Scale parameter. Adjust that value. It will be proportional unless you unlink the x and y scales.