diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index df3199f..91f86c0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -23,7 +23,7 @@ on:
 jobs:
   build:
     name: Build
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         python-version: [ "3.7", "3.8", "3.9", "3.10" ]