diff --git a/.github/workflows/update-test-container-image-references.yml b/.github/workflows/update-test-container-image-references.yml
index 58d5650c..d1282e06 100644
--- a/.github/workflows/update-test-container-image-references.yml
+++ b/.github/workflows/update-test-container-image-references.yml
@@ -14,7 +14,10 @@ jobs:
     - name: Install skopeo
       run: sudo apt-get install -y skopeo
     - name: Run update script
-      run: python3 .ci/update-test-container-image-reference.py
+      run: |
+          # Avoid skopeo trying to write to /run/containers/$USER_ID, which it isn't allowed to do in this context.
+          export REGISTRY_AUTH_FILE="$(mktemp)"
+          python3 .ci/update-test-container-image-reference.py
     - name: Create Pull Request
       uses: peter-evans/create-pull-request@5f6978faf089d4d20b00c7766989d076bb2fc7f1 # v7
       with: