diff --git a/.travis.yml b/.travis.yml
index 5c63b2e..2739861 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-18.03.tar.gz"
-
 script:
-    - nix-build tests/intern.nix
-    - nix-build tests/extern.nix
+    - NIX_PATH="nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-18.03.tar.gz" nix-build tests/intern.nix
+    - NIX_PATH="nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-18.03.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
 
 cache:
   directories:
       - /nix/store
+  timeout: 600