diff --git a/yt_dlp/extractor/generic.py b/yt_dlp/extractor/generic.py
index f5c59a093..33e71d1c5 100644
--- a/yt_dlp/extractor/generic.py
+++ b/yt_dlp/extractor/generic.py
@@ -2370,7 +2370,7 @@ class GenericIE(InfoExtractor):
             'id': flashvars['video_id'],
             'display_id': display_id,
             'title': title,
-            'thumbnail': thumbnail,
+            'thumbnail': urljoin(url, thumbnail),
             'formats': formats,
         }