diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index edd7300c..74d3e14c 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -29,6 +29,10 @@ jobs:
           - ld_prefix: "/usr/local"
           - os: macos-14
             ld_prefix: "/opt/homebrew"
+        # A pull request tests each macOS runner on one Python version, the oldest on the Intel
+        # runner and the newest on the arm64 one, while Ubuntu tests every version; a push to
+        # master or to a stable branch tests the whole matrix.
+        exclude: ${{ github.event_name == 'pull_request' && fromJSON('[{"os":"macos-15-intel","python-version":"3.11"},{"os":"macos-15-intel","python-version":"3.12"},{"os":"macos-15-intel","python-version":"3.13"},{"os":"macos-14","python-version":"3.10"},{"os":"macos-14","python-version":"3.11"},{"os":"macos-14","python-version":"3.12"}]') || fromJSON('[]') }}
 
     steps:
       - name: Checkout