diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c2cf940..632a800 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,7 +38,7 @@ jobs:
         sudo apt-get install -y pristine-tar sbuild mmdebstrap util-linux dpkg-dev
     - name: Setup subuid/subgid
       run: |
-        usermod --add-subuids 100000-200000 --add-subgids 100000-200000 $USER
+        usermod --add-subuids 100000-200000 --add-subgids 100000-200000 ${USER:-root}
     - name: Run tests with verbose logging (timeout 30min)
       env:
         RUST_LOG: debug