iMessage on mac disabling message notifications on iPhone

When my mac laptop is awake, whether the iMessage app is open or not, my iPhone doesn't play audible text alerts. I will still see the banner if I happen to be looking at my phone, but I hear no alert. A message alert will only play through my mac. This is annoying, as I may not be near my mac or I may have the sound muted, as I frequently do, and I miss important messages. Yes, my notification settings are all set correctly. Everything on my iPhone works as it should unless my laptop is awake – as I said, whether or not the iMessage app is open.