diff --git a/.forgejo/workflows/build.yml b/.forgejo/workflows/build.yml
index aa43815..af51cc1 100644
--- a/.forgejo/workflows/build.yml
+++ b/.forgejo/workflows/build.yml
@@ -12,6 +12,14 @@ jobs:
     name: Build & push runner image
     runs-on: docker-cli-node24   # the label of your runner
     steps:
+      - name: Checkout runner Dockerfile only
+        uses: actions/checkout@v5
+        with:
+          sparse-checkout: |
+            .forgejo/runners/Dockerfile
+          sparse-checkout-cone-mode: false
+          fetch-depth: 1
+
       - name: Build & push runner image
         run: |
           docker build --network=host -t ${{ vars.REGISTRY_URL }}/asteroids/runner:latest -f .forgejo/runner/Dockerfile .