This is one of the reasons why I don't use a separate partition for /boot anymore. As I understand it, a separate /boot partition is mostly a legacy thing unless you have an encrypted root partition or some other special setup. For simple cases I recommend having /boot on the root partition to avoid issues like this.

I think that's also the default setup used by the Debian installer if you select Guided partitioning – use entire disk. I'm not 100% sure tho.