diff --git a/.github/workflows/preview-build.yml b/.github/workflows/preview-build.yml
index e24373d26..18595303a 100644
--- a/.github/workflows/preview-build.yml
+++ b/.github/workflows/preview-build.yml
@@ -18,6 +18,7 @@ on:
         default: 'true'
       metadata-only:
         description: 'Only generate documentation metadata files'
+        type: string
         required: false
         default: 'false'
       continue-on-error: