diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 8c625300e8..4ee894e6c6 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -34,7 +34,7 @@ jobs:
         fail_ci_if_error: true
 
   unittest-py36:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         python-version: ['3.6']