diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 96398e2..da2e6e5 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -5,6 +5,9 @@ on:
     branches: [main]
   pull_request:
     branches: ['**']
+  # by hand for any branch: 'Run workflow' in the Actions tab, or
+  # `gh workflow run test.yml --ref <branch>`
+  workflow_dispatch:
 
 # One run per branch/PR at a time. On a PR a newer push cancels the run in
 # progress: only the newest commit's results matter there, and waiting for a