diff --git a/.github/workflows/preview.yaml b/.github/workflows/preview.yaml
index 54eb0fb76..6f0033442 100644
--- a/.github/workflows/preview.yaml
+++ b/.github/workflows/preview.yaml
@@ -65,7 +65,7 @@ jobs:
           VERCEL_ORG_ID: team_tGkWfhEGGelkkqUUm9nXq17r
           VERCEL_PROJECT_ID: QmZRucMRh3GFk1817ZgXjRVuw5fhTspHPHKct3JNQDEPGd
           VERCEL_TOKEN: ${{ secrets.VERCEL_TOKEN }}
-          CODER_DOCS_MAIN_BRANCH: ${{ github.sha }}
+          CODER_DOCS_MAIN_BRANCH: ${{ github.event.pull_request.head.sha }}
 
       - name: Update Deployment
         # If we don't specify always, it won't run this check if failed.