diff --git a/.github/workflows/testing.yml b/.github/workflows/testing.yml
index 99bec6432c..5108e0a46d 100644
--- a/.github/workflows/testing.yml
+++ b/.github/workflows/testing.yml
@@ -81,7 +81,7 @@ jobs:
 
     steps:
     - name: Checkout code
-      uses: actions/checkout@v2
+      uses: actions/checkout@v2.3.4
       with:
         fetch-depth: 0
     - name: Set up Python
@@ -105,7 +105,7 @@ jobs:
     runs-on: ubuntu-18.04
     needs: tests
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v2.3.4
     - name: Get history and tags for SCM versioning to work
       run: |
         git fetch --prune --unshallow