diff --git a/nix/iohk-nix-src.json b/nix/iohk-nix-src.json
index fd25ba3dc69..dbfb0e38b70 100644
--- a/nix/iohk-nix-src.json
+++ b/nix/iohk-nix-src.json
@@ -1,7 +1,7 @@
 {
   "url": "https://github.com/input-output-hk/iohk-nix",
-  "rev": "05d0b642c5d4a77cd645cc250a658d65e4757aae",
-  "date": "2019-07-09T23:18:02+08:00",
-  "sha256": "17r09fxfir9vcs97vii3jasz49ajkjy77xy0013lab1qkyp72vg6",
+  "rev": "ec5463c3c3442ab3d80500af6c9a57310aed79db",
+  "date": "2019-08-09T20:49:52-04:00",
+  "sha256": "0m1f26awc9v7klzmah06x357hn04bxwyaj287aikjqn2gbg2v51m",
   "fetchSubmodules": false
 }
diff --git a/nix/pkgs.nix b/nix/pkgs.nix
index 9de446c1fa2..089030fd817 100644
--- a/nix/pkgs.nix
+++ b/nix/pkgs.nix
@@ -39,6 +39,7 @@ let
       }
       {
         packages.cardano-sl.patches = [ ./patches/cardano-sl.patch ];
+        packages.ekg-wai.components.library.enableSeparateDataOutput = true;
       }
     ];
   };
diff --git a/nix/update-iohk-nix.sh b/nix/update-iohk-nix.sh
index 66cc202cc01..6ed58247028 100755
--- a/nix/update-iohk-nix.sh
+++ b/nix/update-iohk-nix.sh
@@ -5,5 +5,5 @@ set -euo pipefail
 
 NIX_DIR=$(dirname "$0")
 
-nix-prefetch-git https://github.com/input-output-hk/iohk-nix \
+nix-prefetch-git https://github.com/input-output-hk/iohk-nix refs/heads/haskell-nix-cardano-sl \
                  > "$NIX_DIR/iohk-nix-src.json"