diff --git a/.github/workflows/documentation.yml b/.github/workflows/documentation.yml
index 3105420e7..130de95a9 100644
--- a/.github/workflows/documentation.yml
+++ b/.github/workflows/documentation.yml
@@ -25,7 +25,7 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v2
         with:
-          ref: github.event.inputs.ref || ''
+          ref: ${{ github.event.inputs.ref || '' }}
 
       - name: Install node.js v16
         uses: actions/setup-node@v2