diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4e45cd0..ac16c49 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,5 +1,9 @@
 name: Continuous integration
-on: [push, pull_request]
+on:
+  pull_request:
+  push:
+    branches:
+      - main
 jobs:
   ci:
     name: Validate
@@ -15,4 +19,5 @@ jobs:
         with:
           tasks: build check
           docker_repo: stephanmisc/toast
+          read_remote_cache: ${{ github.event_name == 'push' }}
           write_remote_cache: ${{ github.event_name == 'push' }}