diff -ru old/ghc.install new/ghc.install
--- old/ghc.install	2009-05-12 21:08:17.000000000 +0200
+++ new/ghc.install	2009-05-12 21:12:36.000000000 +0200
@@ -4,7 +4,9 @@
     cat << EOF
     ==> Unregistering cabalized packages...
 EOF
-    cd /usr/share/haskell/ && (for a in *; do ghc-pkg unregister --force $a &> /dev/null; done; cd - > /dev/null )
+    if [ -d /usr/share/haskell ]; then
+      cd /usr/share/haskell/ && (for a in *; do ghc-pkg unregister --force $a &> /dev/null; done; cd - > /dev/null )
+    fi
     cat << EOF
     ==> Done.
 EOF