AI declaring war when i change relationship to peace.

Okay, me and another player are neighbourghs and in same coalition. Both countries grab a few states. The other player goes inactive, the coalition dies. I have a right of way for him and the other (now AI) country has peace for me. I change my relationship also to peace and the AI country instantly declares war. That's just insane. No trade embargo or nothing, straight war.

My point is that an AI country shouldn't declare war when i change to peace, especially when he already had the same relationship for me.