diff --git a/.github/workflows/flow.yml b/.github/workflows/flow.yml
index cca1392..6958755 100644
--- a/.github/workflows/flow.yml
+++ b/.github/workflows/flow.yml
@@ -12,10 +12,10 @@ on:
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: ['3.6.x', '3.7.x', 3.8.x']
+        python-version: ['3.5.x', '3.6.x', '3.7.x', 3.8.x']
 
     steps:
     - uses: actions/checkout@v4