diff --git a/cabal2nix.cabal b/cabal2nix.cabal
--- a/cabal2nix.cabal
+++ b/cabal2nix.cabal
@@ -1,5 +1,5 @@
 Name:                   cabal2nix
-Version:                1.64
+Version:                1.65
 Copyright:              Peter Simons, Andres Loeh
 License:                BSD3
 License-File:           LICENSE
@@ -36,8 +36,8 @@
   .
   The only required argument is the path to the cabal file. For example:
   .
-  > cabal2nix http://hackage.haskell.org/packages/archive/cabal2nix/1.64/cabal2nix.cabal
-  > cabal2nix cabal://cabal2nix-1.64
+  > cabal2nix http://hackage.haskell.org/packages/archive/cabal2nix/1.65/cabal2nix.cabal
+  > cabal2nix cabal://cabal2nix-1.65
   .
   If the @--sha256@ option has not been specified, cabal2nix calls
   @nix-prefetch-url@ to determine the hash automatically. This causes
diff --git a/src/Cabal2Nix/Flags.hs b/src/Cabal2Nix/Flags.hs
--- a/src/Cabal2Nix/Flags.hs
+++ b/src/Cabal2Nix/Flags.hs
@@ -5,6 +5,7 @@
 
 configureCabalFlags :: PackageIdentifier -> FlagAssignment
 configureCabalFlags (PackageIdentifier (PackageName name) _)
+ | name == "arithmoi"           = [disable "llvm"]
  | name == "accelerate-examples"= [disable "opencl"]
  | name == "git-annex"          = [ enable "S3", enable "WebDAV", enable "Inotify"
                                   , enable "Dbus", enable "Assistant", enable "Webapp"
diff --git a/src/Cabal2Nix/PostProcess.hs b/src/Cabal2Nix/PostProcess.hs
--- a/src/Cabal2Nix/PostProcess.hs
+++ b/src/Cabal2Nix/PostProcess.hs
@@ -197,6 +197,10 @@
   , "  mkdir -p $out/share/man/man1"
   , "  mv \"$out/\"**\"/man/\"*.1 $out/share/man/man1/"
   , "'';"
+  , "patches = ["
+  , "  # Patch to make xmonad use XMONAD_{GHC,XMESSAGE} (if available)."
+  , "  ./xmonad_ghc_var_0.11.patch"
+  , "];"
   ]
 
 gitAnnexOverrides :: String
diff --git a/src/Distribution/NixOS/Derivation/Cabal.hs b/src/Distribution/NixOS/Derivation/Cabal.hs
--- a/src/Distribution/NixOS/Derivation/Cabal.hs
+++ b/src/Distribution/NixOS/Derivation/Cabal.hs
@@ -72,7 +72,10 @@
   packageId deriv = PackageIdentifier (PackageName (pname deriv)) (version deriv)
 
 renderDerivation :: Derivation -> Doc
-renderDerivation deriv = funargs (map text ("cabal" : inputs)) $$ vcat
+renderDerivation deriv =
+  text "# This file was auto-generated by cabal2nix. Please do NOT edit manually!" $$
+  text "" $$
+  funargs (map text ("cabal" : inputs)) $$ vcat
   [ text ""
   , text "cabal.mkDerivation" <+> lparen <> text "self" <> colon <+> lbrace
   , nest 2 $ vcat