diff --git a/checkout-nixos.sh b/checkout-nixos.sh
index 662bd729818..300deb196c6 100755
--- a/checkout-nixos.sh
+++ b/checkout-nixos.sh
@@ -5,4 +5,5 @@ nix-env -i subversion
 cd /etc/nixos
 svn co https://svn.cs.uu.nl:12443/repos/trace/nixos/trunk nixos
 svn co https://svn.cs.uu.nl:12443/repos/trace/nixpkgs/trunk nixpkgs
-ln -s ../nixpkgs/pkgs nixos/pkgs
+ln -sf ../nixpkgs/pkgs nixos/pkgs
+ln -sf nixpkgs/pkgs/top-level/all-packages.nix install-source.nix