-remap-file not working for generating PCH files?

I'm using clang to generate a PCH (precompiled header) file.
I'm using the generated PCH file to generate a TU with libclang. However,
when the original file from which the PCH file has been generated does no
longer exist, libclang asserts when I try to get instantiation locations
from the TU. Is there a workaround for this?

Secondly, I tried to generate the PCH file with file remapping (using
-remap-file), but clang always used the original file and didn't replace the
contents of the file as specified by the flag. Is this an incompatibility?

Thank you!