diff --git a/.github/workflows/ci-build.yml b/.github/workflows/ci-build.yml
index 60b5d83..0bb7fe8 100644
--- a/.github/workflows/ci-build.yml
+++ b/.github/workflows/ci-build.yml
@@ -25,6 +25,7 @@ on:
 
 jobs:
   build:
+    if: github.event.pull_request.head.repo.full_name == github.repository
     name: "python ${{ matrix.python-version }} tests"
     runs-on: ubuntu-latest
     strategy: