Even when I say no, AI and I are still friends

[Bojevus]

Anyone else having this issue? The AI will propose friendship, I'll click "not at this time," and when I exit the diplomacy screen, we're shown as being friends.

I thought that maybe that was just indicating their disposition toward me, but recently AIs I've said no to have been proposing alliances, so the game clearly thinks we're in a declared friendship.