Question related to include files .inc

Hello,
thank you for providing this package.
I tried to use it to document some legacy fortran code. For this I wrote a project-file.md:
https://github.com/Jonas231/Koko/blob/master/Docs/FORD/project-file.md
A file .f within src_dir tries to INCLUDE "datlen.inc" which is, however, contained in 'Src/include' folder. The message says:

File "/home/jonas/miniconda3/lib/python3.9/site-packages/ford/reader.py", line 410, in include
raise FileNotFoundError(msg)
FileNotFoundError: Can not find include file "datlen.inc".

The .inc file is there:
https://github.com/Jonas231/Koko/blob/master/Src/include/datlen.inc

It is included within this .f-file:
https://github.com/Jonas231/Koko/blob/master/Src/raytrace/insider.f
in Line 58.

Could you please give me a hint on how to solve this issue?

Best regards,
Jonas