$ cabal update Downloading the latest package list from hackage.haskell.org $ cabal install sifflet Resolving dependencies... cabal: cannot configure pango-0.11.1. It requires cairo >=0.11.1 && <0.12 and glib >=0.11.1 && <0.12 For the dependency on cairo >=0.11.1 && <0.12 there are these packages: cairo-0.11.1. However none of them are available. cairo-0.11.1 was excluded because sifflet-lib-1.0 requires cairo ==0.11.0 cairo-0.11.1 was excluded because cairo-0.11.0 was selected instead cairo-0.11.1 was excluded because sifflet-1.0 requires cairo ==0.11.0 For the dependency on glib >=0.11.1 && <0.12 there are these packages: glib-0.11.1. However none of them are available. glib-0.11.1 was excluded because sifflet-lib-1.0 requires glib ==0.11.0 glib-0.11.1 was excluded because glib-0.11.0 was selected instead glib-0.11.1 was excluded because sifflet-1.0 requires glib ==0.11.0 So that's pretty simple. 'sifflet' requires cairo ==0.11.0 and pango. But since pango doesn't work with cairo 0.11.0, the package can't be built. The solution is to ask the sifflet author to adjust the dependencies to be more flexible. http://hackage.haskell.org/package/sifflet Those specific versions of packages are overly constrained. They should follow the PVP, and be thus, 0.11.* -- Don