diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index bca8644..6f90b51 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -1,6 +1,12 @@
 name: Python package
 
-on: [push]
+on:
+  push:
+    branches:
+    - main
+  pull_request:
+    branches:
+    - main
 
 jobs:
   build:
@@ -8,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.7, 3.8]
+        python-version: [3.7, 3.8, 3.9]
 
     steps:
     - uses: actions/checkout@v2