diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 1a1a0a238..c006fa802 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -10,7 +10,7 @@ jobs:
   CodeQL-Build:
     runs-on: ubuntu-18.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
 
       - name: Initialize CodeQL
         uses: github/codeql-action/init@v1
diff --git a/.github/workflows/dev-image.yml b/.github/workflows/dev-image.yml
index 8a78cf342..ea015f4f2 100644
--- a/.github/workflows/dev-image.yml
+++ b/.github/workflows/dev-image.yml
@@ -27,7 +27,7 @@ jobs:
   dev-image-test:
     runs-on: ubuntu-18.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       - name: Login to Packages
         run: echo '${{ secrets.GITHUB_TOKEN }}' | docker login 'docker.pkg.github.com' -u 'peaceiris' --password-stdin
       - run: docker-compose pull --quiet
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index a2541e160..d8de88310 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -9,7 +9,7 @@ jobs:
   release:
     runs-on: ubuntu-18.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       # https://github.com/peaceiris/workflows/blob/main/create-release-npm/action.yml
       - uses: peaceiris/workflows/create-release-npm@v0.8.1
         env:
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 4a2c71a9a..b1d6e26e7 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -21,7 +21,7 @@ jobs:
           - 'macos-latest'
           - 'windows-latest'
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
 
       - name: Dump GitHub context
         env:
diff --git a/.github/workflows/update-major-tag.yml b/.github/workflows/update-major-tag.yml
index c06cab84d..91939f2e3 100644
--- a/.github/workflows/update-major-tag.yml
+++ b/.github/workflows/update-major-tag.yml
@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-18.04
     steps:
 
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v2.3.4
 
     - name: Update major tag
       if: github.event.release.prerelease == false