Trouble doing Mac-to-Mac FaceTime

I have a friend I like to do FaceTime with pretty often. We've been having lots of trouble getting connections between our Macs, FT keeps trying to use our iPhones. Like I'll call him in the FT app on my MacBook and it says "Using iPhone," so I end the call and try again. Or I start a FT and it starts from my Mac but then my friend's iPhone alerts him instead of his iMac.
Somehow we always finally end up on the Macs but does any body know how we can do that right away and keep the iPhones from being used on either end?