diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 6a35ba7..e6dfbea 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -151,6 +151,13 @@ jobs:
                  ndctl='${{ github.workspace }}'/ndctl \
                  ../run_qemu/run_qemu.sh -v --no-run ${{ matrix.run_opts }}
 
+      #  Test update_existing_rootfs(), default value for distro= and various other things
+      - name: incremental build
+        run: |
+          set -x
+          cd kernel
+          ../run_qemu/run_qemu.sh -v --no-run ${{ matrix.run_opts }}
+
       - name: ccache stats post build
         run: |
           # Pre-build stats printed at the start of the build step