diff --git a/.github/workflows/build-docs.yml b/.github/workflows/build-docs.yml
index 1fd1bae68..a5973f192 100644
--- a/.github/workflows/build-docs.yml
+++ b/.github/workflows/build-docs.yml
@@ -42,7 +42,7 @@ jobs:
         if: steps.cache.outputs.cache-hit != 'true'
         run: python3.7 -m flit install --extras doc
       - name: Install Material for MkDocs Insiders
-        if: github.event.pull_request.head.repo.fork == false && steps.cache.outputs.cache-hit != 'true'
+        if: github.event_name == 'pull_request' && github.event.pull_request.head.repo.fork == false && steps.cache.outputs.cache-hit != 'true'
         run: python3.7 -m pip install git+https://${{ secrets.ACTIONS_TOKEN }}@github.com/squidfunk/mkdocs-material-insiders.git
       - uses: actions/cache@v2
         with: