diff --git a/.github/workflows/tox.yml b/.github/workflows/tox.yml
index 749cc273..cb408311 100644
--- a/.github/workflows/tox.yml
+++ b/.github/workflows/tox.yml
@@ -12,7 +12,7 @@ on:
 
 jobs:
   tests:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-18.04
     strategy:
       matrix:
         python-version: ["3.6", "3.8"]