diff --git a/.github/workflows/testing.yml b/.github/workflows/testing.yml
index e3d1ecf8c7d..b2d6c00e09e 100644
--- a/.github/workflows/testing.yml
+++ b/.github/workflows/testing.yml
@@ -99,7 +99,7 @@ jobs:
     container: jasonb87/cime:latest
     strategy:
       matrix:
-        python-version: [3.8, 3.9, 3.10]
+        python-version: ['3.8', '3.9', '3.10']
     steps:
       - name: Checkout code
         uses: actions/checkout@v2