diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e14bf96..8c64662 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,11 +1,17 @@
 name: CI
 
+# Branch pushes are covered by the pull_request trigger. Listening to both for
+# every branch ran the whole matrix twice per PR.
 on:
   push:
-    branches: ['**']
+    branches: [master]
   pull_request:
     branches: ['**']
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 env:
   CARGO_TERM_COLOR: always
   RUST_BACKTRACE: 1