diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index f1353e36..00980b45 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -24,7 +24,7 @@ jobs:
 
   python-format:
     name: python format
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v3
       with: