diff --git a/docs/.vitepress/imgit/plugin/youtube.ts b/docs/.vitepress/imgit/plugin/youtube.ts
index d70e99ff7..c915b0494 100644
--- a/docs/.vitepress/imgit/plugin/youtube.ts
+++ b/docs/.vitepress/imgit/plugin/youtube.ts
@@ -48,7 +48,7 @@ function build(asset: BuiltAsset): boolean {
 }
 
 async function resolveThumbnailUrl(id: string): Promise<string> {
-    if ((<YouTubeCache>cache).youtube.hasOwnProperty(id))
+    if ((<YouTubeCache>cache).youtube?.hasOwnProperty(id))
         return (<YouTubeCache>cache).youtube[id];
     let response: Response;
     for (const variant of thumbs)