diff --git a/.github/workflows/build_doc.yml b/.github/workflows/build_doc.yml
index 9735cd3d3c8..53f673c203d 100644
--- a/.github/workflows/build_doc.yml
+++ b/.github/workflows/build_doc.yml
@@ -65,7 +65,7 @@ jobs:
         if: steps.get_round.outputs.result != 'stop'
         with:
            repository: ${{ github.repository }}
-           ref: refs/pull/${{ steps.get_pr_number.outputs.result }}/merge
+           ref: refs/pull/${{ steps.get_pr_number.outputs.result }}/head
            fetch-depth: 2
 
       - name: install dependencies