diff --git a/.github/workflows/book.yml b/.github/workflows/book.yml
index 43d7f85..758a758 100644
--- a/.github/workflows/book.yml
+++ b/.github/workflows/book.yml
@@ -22,7 +22,7 @@ jobs:
         run: |
           echo ACTION_USER=$USER >> $GITHUB_ENV
 
-      - uses: DeterminateSystems/nix-installer@main
+      - uses: DeterminateSystems/nix-installer-action@2ec668c45628a4029e59357600d6b73107b0843b
         with:
           extra-conf: |
             trusted-users = root ${{ env.ACTION_USER }}
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 8fa8a5a..a6dfa72 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -17,7 +17,7 @@ jobs:
         run: |
           echo ACTION_USER=$USER >> $GITHUB_ENV
 
-      - uses: DeterminateSystems/nix-installer@main
+      - uses: DeterminateSystems/nix-installer-action@2ec668c45628a4029e59357600d6b73107b0843b
         continue-on-error: true # Self-hosted runners already have Nix installed
         with:
           extra-conf: |