Wrong format of $PROJECT_DIR

Hi there !
I recently switched to PlatformIO for my Arduino projects.

I’m currently facing a pretty annoying issue with the $PROJECT_DIR built-in variable :
The address is wrong by one character. Instead of “C:/etc…” I have “c:/…” (lower case c) The compiler is therefore unable to find the included files.

I have tried to mess with the platformio.ini file following the link : Redirecting...
So far nothing seems to work and I’m stuck here.

Does anyone knows of this issue and how to solve it ?

Thank you

Window’s filesystem is case-insensitive, this can’t be.