diff --git a/.github/workflows/ubuntu.yaml b/.github/workflows/ubuntu.yaml
index 29ee79a981f3..f4f83dc2017a 100644
--- a/.github/workflows/ubuntu.yaml
+++ b/.github/workflows/ubuntu.yaml
@@ -6,7 +6,7 @@ jobs:
     container:
       image: openquantumsafe/ci-ubuntu-focal-x86_64:latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # pin@v4
     - name: Set up SSH environment
       run: |
         mkdir -p -m 0755 /var/empty