This reverts commit 4d6452ba. The change affects Hydra in a way we didn't
expect: https://github.com/NixOS/nixpkgs/pull/9305#issuecomment-132791730.
This reverts commit 4d6452ba. The change affects Hydra in a way we didn't
expect: https://github.com/NixOS/nixpkgs/pull/9305#issuecomment-132791730.