diff --git a/youtube_dl/extractor/watchbox.py b/youtube_dl/extractor/watchbox.py
index b382338fa..be0bcba15 100644
--- a/youtube_dl/extractor/watchbox.py
+++ b/youtube_dl/extractor/watchbox.py
@@ -69,7 +69,7 @@ class WatchBoxIE(InfoExtractor):
 
         source = self._parse_json(
             self._search_regex(
-                r'(?s)source\s*:\s*({.+?})\s*,\s*\n', webpage, 'source',
+                r'(?s)source["\']?\s*:\s*({.+?})\s*[,}]', webpage, 'source',
                 default='{}'),
             video_id, transform_source=js_to_json, fatal=False) or {}