diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 308035c6..78c9b94e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -67,7 +67,7 @@ jobs:
     steps:
       - name: Get cache validity period
         id: cache_timestamp
-        run: echo "period=$(($(date +%V) / 4))" >> "$GITHUB_OUTPUT"
+        run: echo "period=$((10#$(date +%V) / 4))" >> "$GITHUB_OUTPUT"
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3