diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 09d3fddde50e987036d588455cca3a177779059c..57eb234d7d8a67b7cc6907ff8bf4ef206f0dfdfa 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -36,8 +36,8 @@           - <YOUR_CACHIX_NAME>
         nixPath:
           - nixpkgs=channel:nixos-unstable
           - nixpkgs=channel:nixpkgs-unstable
-  pull_request:
       - master
+  pull_request:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout repository
@@ -46,6 +46,9 @@     - name: Install nix
       uses: cachix/install-nix-action@v16
       with:
         nix_path: "${{ matrix.nixPath }}"
+        # nix 2.6 breaks restrict-eval, when using the NIX_PATH
+        # see https://github.com/NixOS/nix/issues/5980
+        install_url: https://releases.nixos.org/nix/nix-2.5.1/install
         extra_nix_config: |
           experimental-features = nix-command flakes
           access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}