What Breed Is My Dog?

This is my puppy Bastien. I adopted him from a puppy rescue. They told me he is an Australian Shepherd mix, but that does not seem accurate to me. He looks like a German Shepherd mix to me, but any educated opinions would be very welcome.

For additional info, he is 4 months old and 20 lbs. Some of the pictures make him look stubby, but he actually has long, lean legs. Whatever the mix, he is absolutely adorable, and we love him to pieces :)

By Kohlbe T.