On Mac OS X GHCi 6.0 complains about a missing symbol when trying to load package "util". Wolgang Thaller told me the cause of this bug: The problem was that there was a file called HsReadline.c. The corresponding object file, HsReadline.o, replaced HSreadline.o on the Mac's case-insensitive file system. So the actual problem is a broken readline package, which is used by util. The bug is fixed in the next release (6.0.1) and in CVS. For those who don't feel like compiling CVS-sources, or waiting for the next release; below is a quick fix. A working HSreadline.o is created from the libHSreadline.a file using the -g option of ghc-pkg. 1) set environment variable "libdir" to ghc-6's directory: setenv libdir /usr/local/lib/ghc-6.0/ 2) cp $libdir/libHSreadline.a $libdir/libHSreadline_p.a /tmp/ 3) create a config file for package readline: ghc-pkg -s readline > /tmp/readline.conf 4) cd /tmp 5) remove the package readline from ghc: ghc-pkg -r readline 6) add package again and let ghc-pkg create the ghci library: ghc-pkg -g -a -i /tmp/readline.conf For step 5/6 you may need root-access, use "su" or "sudo" Arthur