diff --git a/.github/workflows/nix-action.yml b/.github/workflows/nix-action.yml
index 28d9de3..9224ff8 100644
--- a/.github/workflows/nix-action.yml
+++ b/.github/workflows/nix-action.yml
@@ -32,7 +32,7 @@ jobs:
           else
             echo "tested_commit=${{ github.sha }}" >> $GITHUB_ENV
           fi
-      - uses: cachix/install-nix-action@v14
+      - uses: cachix/install-nix-action@v16
         with:
           nix_path: nixpkgs=channel:nixpkgs-unstable
       - uses: cachix/cachix-action@v10
@@ -42,6 +42,6 @@ jobs:
           extraPullNames: coq, math-comp
       - uses: actions/checkout@v2
         with:
-          ref: ${{ env.tested_ref }}
+          ref: ${{ env.tested_commit }}
       - run: >
           nix-build https://coq.inria.fr/nix/toolbox --argstr job aac-tactics --arg override '{ ${{ matrix.overrides }}; aac-tactics = builtins.filterSource (path: _: baseNameOf path != ".git") ./.; }'