Installing a dependency with its own local patches doesn't apply them

I have packages A and B, both written by myseld.
B is a dependency of A.
B is using patch-package internally.
When developing B, npm install properly applies the patches.
When adding B to a A, the patch will not be applied.

Any idea what could cause this?
Maybe it's just not the way patch-package is supposed to work?
Tried to search, didn't find anything.