pgindent (probably my missing something obvious)

Hello,

This is the first time I've run pgindent on my current machine, and it
doesn't seem to be making any modifications to source files. For
example this command:

./src/tools/pgindent/pgindent src/backend/optimizer/path/allpaths.c

leaves the allpaths.c file unchanged despite my having some very long
function calls. I've downloaded the latest typedefs list, but I
haven't added any types anyway.

What obvious thing am I missing?

Thanks,
James Coleman