To reproduce:
$ cat foo.pc
prefix=/usr
includedir=${prefix}/include
libdir=${prefix}/lib
Name: foo
Description: Foo library
Version: 1.0.0
Cflags: -I${includedir}
Libs: -L${libdir} -lfo
$ pkgconf --modversion foo.pc
1.0.0
$ pkgconf --validate foo.pc
foo.pc:7: warning: malformed version field with whitespace, trimming to [1.0.0]
Even if we remove the whitespace between the Version:
and the version, it still complains, because it's finding the trailing newline.