diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index f82e21b..9d71eca 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -1,11 +1,19 @@
 name: Build
-on: [push]
+on:
+  push:
+  pull_request:
+    paths-ignore:
+      - '**.md'
 
 jobs:
 
   build:
     name: Build
     runs-on: ubuntu-latest
+    # https://github.com/orgs/community/discussions/57827
+    if: github.event_name != 'pull_request' ||
+      github.event.pull_request.head.repo.full_name !=
+      github.event.pull_request.base.repo.full_name
 
     steps: