diff --git a/pkgs/development/compilers/ghc/8.6.1.nix b/pkgs/development/compilers/ghc/8.6.1.nix
index 7fcb52969151..36ef9d0cc73d 100644
--- a/pkgs/development/compilers/ghc/8.6.1.nix
+++ b/pkgs/development/compilers/ghc/8.6.1.nix
@@ -2,7 +2,7 @@
 
 # build-tools
 , bootPkgs, alex, happy, hscolour
-, autoconf, automake, coreutils, fetchurl, perl, python3, m4
+, autoconf, automake, coreutils, fetchurl, fetchpatch, perl, python3, m4
 
 , libiconv ? null, ncurses
 
@@ -90,6 +90,12 @@ stdenv.mkDerivation (rec {
 
   outputs = [ "out" "doc" ];
 
+  patches = [(fetchpatch rec { # https://phabricator.haskell.org/D5123
+    url = "http://tarballs.nixos.org/sha256/${sha256}";
+    name = "D5123.diff";
+    sha256 = "0nhqwdamf2y4gbwqxcgjxs0kqx23w9gv5kj0zv6450dq19rji82n";
+  })];
+
   postPatch = "patchShebangs .";
 
   # GHC is a bit confused on its cross terminology.