diff --git a/.github/workflows/coverage.yaml b/.github/workflows/coverage.yaml
index 31a4ee7..eb63a9f 100644
--- a/.github/workflows/coverage.yaml
+++ b/.github/workflows/coverage.yaml
@@ -15,7 +15,7 @@ jobs:
     timeout-minutes: 30
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
 
       - uses: actions-rs/toolchain@v1
         with:
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index b8af845..5e04f99 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -7,7 +7,7 @@ jobs:
     name: test on nightly
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v2.3.4
     # Because we use nightly features for building docs,
     # using --all-features will fail without nightly toolchain.
     - uses: actions-rs/toolchain@v1