diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 42e95a07a3c1..48d69eeaea4a 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -62,7 +62,7 @@ jobs:
           merged-as-untrusted-at: ${{ inputs.mergedSha }}
           target-as-trusted-at: ${{ inputs.targetSha }}
 
-      - uses: cachix/install-nix-action@4e002c8ec80594ecd40e759629461e26c8abed15 # v31
+      - uses: cachix/install-nix-action@2126ae7fc54c9df00dd18f7f18754393182c73cd # v31.9.1
         with:
           # Sandbox is disabled on MacOS by default.
           extra_nix_config: sandbox = true
diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index 8ce770139c9b..a99236d2e7c4 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -85,7 +85,7 @@ jobs:
           merged-as-untrusted-at: ${{ inputs.mergedSha }}
           target-as-trusted-at: ${{ inputs.targetSha }}
 
-      - uses: cachix/install-nix-action@4e002c8ec80594ecd40e759629461e26c8abed15 # v31
+      - uses: cachix/install-nix-action@2126ae7fc54c9df00dd18f7f18754393182c73cd # v31.9.1
 
       - uses: cachix/cachix-action@3ba601ff5bbb07c7220846facfa2cd81eeee15a1 # v16
         continue-on-error: true
diff --git a/.github/workflows/eval.yml b/.github/workflows/eval.yml
index 6928e9ae7d32..307ba4442540 100644
--- a/.github/workflows/eval.yml
+++ b/.github/workflows/eval.yml
@@ -132,7 +132,7 @@ jobs:
             core.info(`Found pinned.json commit: ${ciPinBumpCommit}`)
 
       - name: Install Nix
-        uses: cachix/install-nix-action@4e002c8ec80594ecd40e759629461e26c8abed15 # v31
+        uses: cachix/install-nix-action@2126ae7fc54c9df00dd18f7f18754393182c73cd # v31.9.1
 
       - name: Load supported versions
         id: versions
@@ -180,7 +180,7 @@ jobs:
           target-as-trusted-at: ${{ inputs.targetSha }}
 
       - name: Install Nix
-        uses: cachix/install-nix-action@4e002c8ec80594ecd40e759629461e26c8abed15 # v31
+        uses: cachix/install-nix-action@2126ae7fc54c9df00dd18f7f18754393182c73cd # v31.9.1
 
       - uses: cachix/cachix-action@3ba601ff5bbb07c7220846facfa2cd81eeee15a1 # v16
         continue-on-error: true
@@ -270,7 +270,7 @@ jobs:
           merge-multiple: true
 
       - name: Install Nix
-        uses: cachix/install-nix-action@4e002c8ec80594ecd40e759629461e26c8abed15 # v31
+        uses: cachix/install-nix-action@2126ae7fc54c9df00dd18f7f18754393182c73cd # v31.9.1
 
       - name: Combine all output paths and eval stats
         run: |
@@ -451,7 +451,7 @@ jobs:
           merged-as-untrusted-at: ${{ inputs.mergedSha }}
 
       - name: Install Nix
-        uses: cachix/install-nix-action@4e002c8ec80594ecd40e759629461e26c8abed15 # v31
+        uses: cachix/install-nix-action@2126ae7fc54c9df00dd18f7f18754393182c73cd # v31.9.1
 
       - name: Ensure flake outputs on all systems still evaluate
         run: nix flake check --all-systems --no-build './nixpkgs/untrusted?shallow=1'
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 0941cedf98b5..fee21209f727 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -35,7 +35,7 @@ jobs:
         with:
           merged-as-untrusted-at: ${{ inputs.mergedSha }}
 
-      - uses: cachix/install-nix-action@4e002c8ec80594ecd40e759629461e26c8abed15 # v31
+      - uses: cachix/install-nix-action@2126ae7fc54c9df00dd18f7f18754393182c73cd # v31.9.1
 
       # TODO: Figure out how to best enable caching for the treefmt job. Cachix won't work well,
       # because the cache would be invalidated on every commit - treefmt checks every file.
@@ -70,7 +70,7 @@ jobs:
         with:
           merged-as-untrusted-at: ${{ inputs.mergedSha }}
 
-      - uses: cachix/install-nix-action@4e002c8ec80594ecd40e759629461e26c8abed15 # v31
+      - uses: cachix/install-nix-action@2126ae7fc54c9df00dd18f7f18754393182c73cd # v31.9.1
 
       - uses: cachix/cachix-action@3ba601ff5bbb07c7220846facfa2cd81eeee15a1 # v16
         continue-on-error: true
@@ -100,7 +100,7 @@ jobs:
           merged-as-untrusted-at: ${{ inputs.mergedSha }}
           target-as-trusted-at: ${{ inputs.targetSha }}
 
-      - uses: cachix/install-nix-action@4e002c8ec80594ecd40e759629461e26c8abed15 # v31
+      - uses: cachix/install-nix-action@2126ae7fc54c9df00dd18f7f18754393182c73cd # v31.9.1
 
       - uses: cachix/cachix-action@3ba601ff5bbb07c7220846facfa2cd81eeee15a1 # v16
         continue-on-error: true