Blanket won't stay on!

[Kanny08]

Hi my son is 4 years old and in his own room. When he's sleeping he moves a lot so his duvet comes off and then he calls for me to put it back on him. How cn I teach him to put it back himself at night when it comes off.? Thanks

[ARoseDowntown]

Hate this. I’ve replaced the duvet with blankets and tuck them in really tightly. It’s the only thing that works.