4/5am wake up

I decided to stop feeding my 20 month old overnight, so now he just has breastmilk during awake hours of the day. It’s going fairly well, we’ve managed to drop all the feeds with some serious persistence. BUT, it has been maybe a month now and he refuses to sleep through, he still keeps waking at 4/5am. This leads to a screaming match, he wants milk and seeing me just makes the situation 10 times worse. It takes almost an hour to resettle him, I keep having to go back in and reinforce the fact he won’t get milk and that it is sleep time. He’ll cuddle me and settle but will start crying again in the cot. Any tips on how to help him sleep through? Or do I just need to be persistent and eventually he’ll get the message and resettle? He’ll resettle independently at other times of the night.