diff --git a/cabal2nix.cabal b/cabal2nix.cabal
--- a/cabal2nix.cabal
+++ b/cabal2nix.cabal
@@ -1,5 +1,5 @@
 name:               cabal2nix
-version:            2.15.4
+version:            2.15.5
 synopsis:           Convert Cabal files into Nix build instructions.
 description:
   Convert Cabal files into Nix build instructions. Users of Nix can install the latest
diff --git a/src/Distribution/Nixpkgs/Fetch.hs b/src/Distribution/Nixpkgs/Fetch.hs
--- a/src/Distribution/Nixpkgs/Fetch.hs
+++ b/src/Distribution/Nixpkgs/Fetch.hs
@@ -77,7 +77,7 @@
   pPrint DerivationSource {..} =
     let isHackagePackage = "mirror://hackage/" `L.isPrefixOf` derivUrl
         fetched = derivKind /= ""
-    in if isHackagePackage then attr "sha256" $ string derivHash
+    in if isHackagePackage then if derivHash /= "" then attr "sha256" $ string derivHash else mempty
        else if not fetched then attr "src" $ text derivUrl
             else vcat
                  [ text "src" <+> equals <+> text ("fetch" ++ derivKind) <+> lbrace
diff --git a/src/Distribution/Nixpkgs/Haskell/Derivation.hs b/src/Distribution/Nixpkgs/Haskell/Derivation.hs
--- a/src/Distribution/Nixpkgs/Haskell/Derivation.hs
+++ b/src/Distribution/Nixpkgs/Haskell/Derivation.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE TemplateHaskell #-}
@@ -9,13 +8,17 @@
   , extraFunctionArgs, libraryDepends, executableDepends, testDepends, configureFlags
   , cabalFlags, runHaddock, jailbreak, doCheck, doBenchmark, testTarget, hyperlinkSource, enableSplitObjs
   , enableLibraryProfiling, enableExecutableProfiling, phaseOverrides, editedCabalFile, metaSection
-  , dependencies, setupDepends, benchmarkDepends, enableSeparateDataOutput
+  , dependencies, setupDepends, benchmarkDepends, enableSeparateDataOutput, extraAttributes
   )
   where
 
+import Prelude hiding ((<>))
+
 import Control.DeepSeq
 import Control.Lens
 import Data.List ( isPrefixOf )
+import Data.Map ( Map )
+import qualified Data.Map as Map
 import Data.Set ( Set )
 import qualified Data.Set as Set
 import Data.Set.Lens
@@ -29,10 +32,6 @@
 import Language.Nix
 import Language.Nix.PrettyPrinting
 
-#if MIN_VERSION_base(4,11,0)
-import Prelude hiding ((<>))
-#endif
-
 -- | A represtation of Nix expressions for building Haskell packages.
 -- The data type correspond closely to the definition of
 -- 'PackageDescription' from Cabal.
@@ -45,6 +44,7 @@
   , _isLibrary                  :: Bool
   , _isExecutable               :: Bool
   , _extraFunctionArgs          :: Set Binding
+  , _extraAttributes            :: Map String String
   , _setupDepends               :: BuildInfo
   , _libraryDepends             :: BuildInfo
   , _executableDepends          :: BuildInfo
@@ -77,6 +77,7 @@
   , _isLibrary = error "undefined Derivation.isLibrary"
   , _isExecutable = error "undefined Derivation.isExecutable"
   , _extraFunctionArgs = error "undefined Derivation.extraFunctionArgs"
+  , _extraAttributes = error "undefined Derivation.extraAttributes"
   , _setupDepends = error "undefined Derivation.setupDepends"
   , _libraryDepends = error "undefined Derivation.libraryDepends"
   , _executableDepends = error "undefined Derivation.executableDepends"
@@ -138,6 +139,7 @@
       , boolattr "hyperlinkSource" (not _hyperlinkSource) _hyperlinkSource
       , onlyIf (not (null _phaseOverrides)) $ vcat ((map text . lines) _phaseOverrides)
       , pPrint _metaSection
+      , vcat [ attr k (text v) | (k,v) <- Map.toList _extraAttributes ]
       ]
     , rbrace
     ]
diff --git a/src/Distribution/Nixpkgs/Haskell/FromCabal.hs b/src/Distribution/Nixpkgs/Haskell/FromCabal.hs
--- a/src/Distribution/Nixpkgs/Haskell/FromCabal.hs
+++ b/src/Distribution/Nixpkgs/Haskell/FromCabal.hs
@@ -83,6 +83,7 @@
     & isLibrary .~ isJust library
     & isExecutable .~ not (null executables)
     & extraFunctionArgs .~ mempty
+    & extraAttributes .~ mempty
     & libraryDepends .~ foldMap (convertBuildInfo . libBuildInfo) (maybeToList library ++ subLibraries)
     & executableDepends .~ mconcat (map (convertBuildInfo . buildInfo) executables)
     & testDepends .~ mconcat (map (convertBuildInfo . testBuildInfo) testSuites)