This is a sid-only issue. Please binNMU the following packages on i386 and amd64, in this order: haskell-happs-util haskell-happs-data haskell-happs-state haskell-happs-ixset haskell-happs-server Each one build-depends on the previous and the last one will close #507631. HAppS is currently uninstallable since it has a versioned dependency on hslogger. binNMUs should be enough to bump that dep.