diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index 12f6431..d641e6b 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -7,8 +7,13 @@ jobs:
   tests:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: DeterminateSystems/nix-installer-action@v16
+      - uses: actions/checkout@v7
+      - uses: DeterminateSystems/nix-installer-action@v22
+        with:
+          # Upstream Nix, not Determinate Nix: the action has
+          # defaulted determinate to true since v21, and this
+          # project targets the Nix everyone else runs.
+          determinate: false
       - name: builtins-only lint
         run: |
           if grep -RnE '(^|[^a-zA-Z_.])(lib|pkgs)[.]' lib; then
@@ -24,8 +29,13 @@ jobs:
     runs-on: ubuntu-latest
     continue-on-error: true
     steps:
-      - uses: actions/checkout@v4
-      - uses: DeterminateSystems/nix-installer-action@v16
+      - uses: actions/checkout@v7
+      - uses: DeterminateSystems/nix-installer-action@v22
+        with:
+          # Upstream Nix, not Determinate Nix: the action has
+          # defaulted determinate to true since v21, and this
+          # project targets the Nix everyone else runs.
+          determinate: false
       - run: |
           nix eval 'github:nix-caisson/caisson-compat#lib.caisson-compat.tests.summary' \
             --override-input caisson-core "path:$PWD"