diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 20c251b..77fee36 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -32,7 +32,7 @@ jobs:
         with:
           oauth-client-id: ${{ secrets.TS_OAUTH_CLIENT_ID }}
           oauth-secret: ${{ secrets.TS_OAUTH_SECRET }}
-          hostname: github-actions-${{ matrix.system }}
+          hostname: github-actions-${{ replace(matrix.system, '_', '-') }}
           tags: tag:ci
 
       - name: Check if Attic endpoint is reachable