diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 88aae4e..8336e5d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,7 +7,7 @@ on:
 
 jobs:
   flake8:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v3
       - name: set up python
@@ -19,7 +19,7 @@ jobs:
       - name: lint with flake8
         run: flake8 --statistics shentry.py
   run-tests:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         pythonversion: ['2.7', '3.5', '3.6', '3.7', '3.8', '3.9', '3.10', '3.11', '3.12']