diff --git a/.travis.yml b/.travis.yml
index 7167f5e..3020384 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,11 +1,11 @@
 language: nix
+env:
+  NIX_PATH="nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-17.09.tar.gz"
+
 script:
-    - NIX_PATH="nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-17.09.tar.gz" nix-build tests/intern.nix
-    - NIX_PATH="nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-17.09.tar.gz" nix-build tests/extern.nix
-    - NIX_PATH="nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-unstable.tar.gz" nix-build tests/intern.nix
-    - NIX_PATH="nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-unstable.tar.gz" nix-build tests/extern.nix
+    - nix-build tests/intern.nix
+    - nix-build tests/extern.nix
 
 cache:
   directories:
       - /nix/store
-  timeout: 600