The worst are inexperienced product managers who look at you like you're trying to pull a fast one.

If it's something small, then maybe just code it up quick in a branch named after the PM-Feature (so you can keep track). Then ask them to validate the requirement before you merge it in (hopefully you can help with this). At least this way they know that you aren't being lazy etc.

Next time that PM asks for something "simple", do a quick branch list of invalidated feature requests.