1.21.5 trying to detect if a player is wearing specific armor

I'm trying to apply potion effects to players wearing specific armor and the following command works in 1.21.4

/effect give @a[nbt={Inventory:[{Slot:103b,id:"minecraft:diamond_helmet"}]}] minecraft:water_breathing 1 0 true

This doesn't work in 1.21.5, the command will still run but it will say no player is detected even if there should be. I assume this might have something to do with how they changed equipment but I have yet to find the correct solution.