diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index f812846..66d63c8 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -27,7 +27,7 @@ jobs:
         uses: jupyterhub/action-major-minor-tag-calculator@v3
         with:
           githubToken: ${{ secrets.GITHUB_TOKEN }}
-          prefix: "${{ env.name }}"
+          prefix: "${{ env.name }}:"
       - name: Docker metadata
         id: meta
         uses: docker/metadata-action@v4