diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 796d3ef..f02cd73 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -32,4 +32,4 @@ jobs:
         if [ -n "$(nbdev_diff_nbs)" ]; then echo -e "!!! Detected difference between the notebooks and the library"; false; fi
     - name: Run tests
       run: |
-        nbdev_test_nbs --fname "nbs/0*.ipynb"  
+        nbdev_test_nbs --fname "nbs/0*.ipynb" --n_workers=1