Unregistering a package

I have an interesting problem. There are two versions of the HsDNS package installed right now: $ ghc-pkg list | /usr/local/ghc-current/lib/ghc-6.5/package.conf: | rts-1.0, [...] (hsdns-2005-02-04), | hsdns-2005-02-08 Now how can I unregister them? I have tried everything I could think of, but no luck: $ ghc-pkg unregister hsdns | ghc-pkg: package hsdns matches multiple packages: | hsdns-2005-02-04, hsdns-2005-02-08 $ ghc-pkg unregister hsdns-2005-02-08 | ghc-pkg: cannot parse 'hsdns-2005-02-08' as a package identifier Can someone give me a pointer how to remedy this situation? Peter