diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 8f81705b..e682e05d 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -1,6 +1,10 @@
 name: govuk-docker
 
-on: push
+on:
+  pull_request:
+  push:
+    branches:
+      - master
 
 jobs:
   test: