Xcode, Warning: no rule to process

I get a lot of warnings in xcode I don’t quite understand like the following.
warning: no rule to process file ‘/Users/davidgunnarsson/code/DrumR/Source/Compressor.h’ of type sourcecode.c.h for architecture i386

Pretty much one per sourcefile. What is it about, can I suppress it?

Have you ticked the boxes in Projucer that forces it to try to compile those files? In almost all cases .h files should be added to your project but not actually marked as being compiled.

Yes it was as simple as that. Not sure how all those got checked in the first place but fixing was easy.