diff --git a/.github/workflows/openapi.yml b/.github/workflows/openapi.yml
index f00bb9e9b..d3dfd0a6a 100644
--- a/.github/workflows/openapi.yml
+++ b/.github/workflows/openapi.yml
@@ -50,7 +50,7 @@ jobs:
         run: |
           git remote add upstream https://github.com/${{ github.event.pull_request.base.repo.full_name }}
           git -c protocol.version=2 fetch --prune --progress --no-recurse-submodules upstream +refs/heads/*:refs/remotes/upstream/* +refs/tags/*:refs/tags/*
-          ANCESTOR_REF=$(git merge-base upstream/${{ github.base_ref }} origin/${{ $HEAD_REF }})
+          ANCESTOR_REF=$(git merge-base upstream/${{ github.base_ref }} origin/$HEAD_REF)
           git checkout --progress --force $ANCESTOR_REF
       - name: Setup .NET
         uses: actions/setup-dotnet@3447fd6a9f9e57506b15f895c5b76d3b197dc7c2 # v3.2.0