diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index d27effdd4..534f4ce3c 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -9,6 +9,9 @@ jobs:
     - uses: cachix/install-nix-action@v16
       with:
         nix_path: nixpkgs=channel:nixos-unstable
+        # 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
     - run: ./ci/test.sh
diff --git a/.github/workflows/update.yml b/.github/workflows/update.yml
index fd038fbc5..28b6372bb 100644
--- a/.github/workflows/update.yml
+++ b/.github/workflows/update.yml
@@ -17,6 +17,9 @@ jobs:
     - uses: cachix/install-nix-action@v16
       with:
         nix_path: nixpkgs=channel:nixos-unstable
+        # 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
     - name: update nur / nur-combined