diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 7d2ae4b..f5a75de 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -6,7 +6,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: np-complete/build-book-action@v1
         with:
           config: config.ebook.yml
diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index fc3a8fd..fbcb062 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -10,5 +10,5 @@ jobs:
     if: github.event.pull_request.merged == true
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: np-complete/publish-book-action@v1