diff --git a/.travis.yml b/.travis.yml
index dc6c86a95ad..2361df40357 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,11 +5,16 @@ env:
 
 install:
   - nix-env -iA nixopsUnstable -f '<nixpkgs>'
+  - cat /etc/nix/nix.conf > ~/nix.conf
+  - echo "binary-caches = https://cache.nixos.org https://hydra.iohk.io https://hydra.angeldsis.com" > ~/nix.conf
+  - echo "binary-cache-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=" > ~/nix.conf
+  - export NIX_CONF_DIR=~
   - touch static/datadog-{api,application}.secret
   - echo "secret" > static/tarsnap-cardano-deployer.secret
   - mkdir keys
   - touch keys/key{0,1,2,3,4,5,6,7,8,9,10,11,12,13,41}.sk
 script:
+  - env
   - nixops --version
   # check all scripts compile
   - ./CardanoCSL.hs --help
@@ -31,6 +36,7 @@ script:
   - nixops deploy -d csl-explorer-staging --evaluate-only --show-trace
   - nixops deploy -d tw --evaluate-only --show-trace
   - nixops deploy -d inf --evaluate-only --show-trace
+  - nix-shell -p cabal2nix stack cabal-install ghc -Q -j 4 --run scripts/check-stack2nix.sh
 
 notifications:
   email: false
diff --git a/default.nix b/default.nix
index 67bd9aeeba9..12814613211 100644
--- a/default.nix
+++ b/default.nix
@@ -11,7 +11,7 @@ let
     configureFlags = flags;
   });
   socket-io-src = pkgs.fetchgit (removeAttrs (importJSON ./pkgs/engine-io.json) ["date"]);
-in (import pkgs/default.nix { inherit pkgs compiler; }).override {
+in ((import pkgs/default.nix { inherit pkgs compiler; }).override {
   overrides = self: super: {
     cardano-sl-core = prodMode super.cardano-sl-core;
     cardano-sl = overrideCabal super.cardano-sl (drv: {
@@ -52,4 +52,7 @@ in (import pkgs/default.nix { inherit pkgs compiler; }).override {
     #enableLibraryProfiling = false;
     #});
   };
+}) // {
+  # extra packages to expose, that have no relation to pkgs/default.nix
+  stack2nix = compiler.callPackage ./pkgs/stack2nix.nix {};
 }
diff --git a/jobsets/cardano.nix b/jobsets/cardano.nix
index 3b028988f0d..21c241c7dac 100644
--- a/jobsets/cardano.nix
+++ b/jobsets/cardano.nix
@@ -5,8 +5,7 @@ with pkgs;
 let
   iohkpkgs = import ./../default.nix {};
 in rec {
-  inherit (iohkpkgs) cardano-report-server-static cardano-sl-static cardano-sl-explorer-static cardano-sl;
-  stack2nix = iohkpkgs.callPackage ./../pkgs/stack2nix.nix {};
+  inherit (iohkpkgs) cardano-report-server-static cardano-sl-static cardano-sl-explorer-static cardano-sl stack2nix;
   cardano-node-image = (import <nixpkgs/nixos/lib/eval-config.nix> {
     system = "x86_64-linux";
     modules = [
diff --git a/nixpkgs-src.json b/nixpkgs-src.json
index 879972c7b98..01c420a57f7 100644
--- a/nixpkgs-src.json
+++ b/nixpkgs-src.json
@@ -1,6 +1,6 @@
 {
     "owner":  "NixOS",
     "repo":   "nixpkgs",
-    "rev":    "464c79ea9f929d1237dbc2df878eedad91767a72",
-    "sha256": "05kkm978bfai3krsjn6h310xj7q0022bbh7a80kdizglqfkj8krw"
+    "rev":    "c0b1e8a5fb174cd405dcca9f7fec275714ad9f4b",
+    "sha256": "019qda3brga12d74545i5pcc74awsc1zkvgdfy6fycsv44kyrn6q"
 }
diff --git a/pkgs/default.nix b/pkgs/default.nix
index 94d20ac892a..902e3d0af70 100644
--- a/pkgs/default.nix
+++ b/pkgs/default.nix
@@ -3448,8 +3448,8 @@ self: {
           pname = "exceptions";
           version = "0.8.3";
           sha256 = "1gl7xzffsqmigam6zg0jsglncgzxqafld2p6kb7ccp9xirzdjsjd";
-          revision = "1";
-          editedCabalFile = "fc13261461399b8610d60468757f2fc0a62ed660dee998f4329e33dd76d2191b";
+          revision = "2";
+          editedCabalFile = "dc2b4ed2a3de646d8ff599ff972e25b3a1a5165ead3a46ff84a3d443814c85ee";
           libraryHaskellDepends = [
             base
             mtl
@@ -5454,6 +5454,8 @@ self: {
           pname = "natural-transformation";
           version = "0.4";
           sha256 = "1by8xwjc23l6pa9l4iv7zp82dykpll3vc3hgxk0pgva724n8xhma";
+          revision = "1";
+          editedCabalFile = "83bedd2c7b0e4f8819753d2075036d99483d33bfdd3ba8889cf61fa05fa89ce9";
           libraryHaskellDepends = [
             base
           ];
diff --git a/scripts/check-stack2nix.sh b/scripts/check-stack2nix.sh
new file mode 100755
index 00000000000..8b853c5df11
--- /dev/null
+++ b/scripts/check-stack2nix.sh
@@ -0,0 +1,16 @@
+#!/bin/bash
+
+
+# Get relative path to script directory
+set -xe
+scriptDir=$(dirname -- "$(readlink -f -- "${BASH_SOURCE[0]}")")
+
+time nix-build -A stack2nix -o $scriptDir/stack2nix -Q -j 4
+
+#time $scriptDir/stack2nix/bin/stack2nix --revision 4bcf1e6b601d531f753ebdb6aec23e19d4b08e6c https://github.com/input-output-hk/cardano-sl.git > $scriptDir/default-2.nix
+
+#diff -u pkgs/default.nix $scriptDir/default-2.nix
+
+source ${scriptDir}/../pkgs/generate.sh
+
+git diff --text --exit-code