How does -I work?

[Pokeman2003]

For some reason, -I"C:\Users\USER\Desktop\Commander\PET\Shared\" doesn't seem to actually add the include. I have a file called MAP in there. Without the -I, the command results in this error. Okay, fair enough.

"C:\Passthrough\VICE\Tools\WLADx\wla-6502.exe" -v2  -o "C:\Users\USER\AppData\Local\Temp\dump\init.o" "C:\Users\USER\Desktop\Commander\PET\Loader File\init.6502"
ERROR ASSEMBLING!
C:\Users\USER\Desktop\Commander\PET\Loader File\init.6502:2: FIND_FILE: Could not open "MAP", searched in the following directories:
./ (current directory)
C:\Users\USER\Desktop\Commander\PET\Loader File\init.6502:2: ERROR: Couldn't parse ".INCLUDE".

Attempting to add the -I line before the -o results in this really peculiar error.

C:\Passthrough\VICE\Tools\WLADx\wla-6502.exe" -v2 -I"C:\Users\USER\Desktop\Commander\PET\Shared\" -o "C:\Users\USER\AppData\Local\Temp\dump\init.o" "C:\Users\USER\Desktop\Commander\PET\Loader File\init.6502"
ERROR ASSEMBLING!
FIND_FILE: Could not open "File\init.6502 ", searched in the following directories:
C:/Users/USER/Desktop/Commander/PET/Shared" -o C:/Users/USER/AppData/Local/Temp/dump/init.o C:/Users/USER/Desktop/Commander/PET/Loader/
./ (current directory)

[Pokeman2003]

It doesn't do leading slashes on the directories.
-I"C:\Users\Schoolwork\Desktop\Commander\PET\Shared" works.

More specifically, it treats \ as an escape character, which means -I"C:\Users\Schoolwork\Desktop\Commander\PET\Shared/" also technically works. Lovely.