diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index ba28701bd..e19b31ca1 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -46,7 +46,7 @@ jobs:
       - name: Run tests
         # Run the tests directly from the source dir so support files (eg, .wav files etc)
         # can be found - they aren't installed into the Python tree.
-        run: python pywin32_testall.py -v -skip-adodbapi
+        run: python -X dev pywin32_testall.py -v -skip-adodbapi
 
       - name: Build wheels
         run: |