[cvs-nhc98] *.hi files

I have trouble understanding the relationship between the .hi file below nhc98/include/ and the ones of the same name generated during the build process (below nhc98/src/prelude, IIRC). Could somebody please enlighten me? My concrete problem is that I've changed CTypesExtra (types => newtypes and added quite a few instances), but the changes don't seem to have any effect for the nhc98 which is being built. :-( Cheers, S.