So here's the problem: We have a Haskell binding to a C library (one of the gtk extension libs) which uses the pthread library. So we put "pthread" in the extra_libraries section of our ghc package conf file. This works fine when building standalone programs, however when we try and use this package in ghci we get this error: ... Loading package gtk2 ... linking ... done. Loading package sourceview ... ghc-6.2.1: can't load .so/.DLL for: pthread (/usr/lib/libpthread.so: invalid ELF header) Inspecting /usr/lib/libpthread.so we find that indeed it is not a .so file but a gnu ld script: /* GNU ld script Use the shared library, but some functions are only in the static library, so try that secondarily. */ OUTPUT_FORMAT(elf32-i386) GROUP ( /lib/libpthread.so.0 /usr/lib/libpthread_nonshared.a ) So we should get ghci to dynamically load /lib/libpthread.so.0, however there is no way to specify this in the package.conf file. It turns out that we don't need ghci to load this .so because it is a dep of another .so that we do load, however if I leave it out then building standalone progs would fail to link. Has anyone come across this before? How do you deal with it? Duncan