diff --git a/cabal2nix.cabal b/cabal2nix.cabal
--- a/cabal2nix.cabal
+++ b/cabal2nix.cabal
@@ -3,7 +3,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           cabal2nix
-version:        2.4
+version:        2.4.1
 synopsis:       Convert Cabal files into Nix build instructions.
 description:    Convert Cabal files into Nix build instructions. Users of Nix can install the latest version by running:
                 .
diff --git a/src/Distribution/Nixpkgs/Haskell/FromCabal/PostProcess.hs b/src/Distribution/Nixpkgs/Haskell/FromCabal/PostProcess.hs
--- a/src/Distribution/Nixpkgs/Haskell/FromCabal/PostProcess.hs
+++ b/src/Distribution/Nixpkgs/Haskell/FromCabal/PostProcess.hs
@@ -103,6 +103,7 @@
   , ("qtah-cpp-qt5", set (libraryDepends . system . contains (bind "pkgs.qt5.qtbase")) True)
   , ("qtah-qt5", set (libraryDepends . tool . contains (bind "pkgs.qt5.qtbase")) True)
   , ("readline", over (libraryDepends . system) (Set.union (pkgs ["readline", "ncurses"])))
+  , ("sbv > 7", set (testDepends . system . contains (pkg "z3")) True)
   , ("sdr", over (metaSection . platforms) (Set.filter (\(Platform arch _) -> arch == X86_64))) -- https://github.com/adamwalker/sdr/issues/2
   , ("shake-language-c", set doCheck False) -- https://github.com/samplecount/shake-language-c/issues/26
   , ("ssh", set doCheck False) -- test suite runs forever, probably can't deal with our lack of network access
diff --git a/src/Distribution/Nixpkgs/Haskell/PackageSourceSpec.hs b/src/Distribution/Nixpkgs/Haskell/PackageSourceSpec.hs
--- a/src/Distribution/Nixpkgs/Haskell/PackageSourceSpec.hs
+++ b/src/Distribution/Nixpkgs/Haskell/PackageSourceSpec.hs
@@ -14,6 +14,7 @@
 import Distribution.Nixpkgs.Hashes
 import qualified Distribution.Nixpkgs.Haskell.Hackage as DB
 import qualified Distribution.Package as Cabal
+import qualified Distribution.Version as Cabal
 import Distribution.PackageDescription
 import qualified Distribution.PackageDescription as Cabal
 import Distribution.Text ( simpleParse, display )
@@ -56,8 +57,13 @@
   pkgId = fromMaybe (error ("invalid Haskell package id " ++ show pkg)) (simpleParse pkg)
   name = Cabal.unPackageName (Cabal.packageName pkgId)
 
+  version :: [Int]
+  version = Cabal.versionNumbers $ Cabal.packageVersion pkgId
+
   lookupVersion :: DB.Map DB.Version Cabal.GenericPackageDescription -> Maybe Cabal.GenericPackageDescription
-  lookupVersion = fmap snd . listToMaybe . reverse . DB.toAscList
+  -- No version is specified, pick latest one
+  lookupVersion m | [] <- version  = fmap snd . listToMaybe $ DB.toDescList m
+  lookupVersion m = DB.lookup (DB.makeVersion version) m
 
 readFileMay :: String -> IO (Maybe String)
 readFileMay file = do