diff --git a/youtube_dl/YoutubeDL.py b/youtube_dl/YoutubeDL.py
index 3cabfbc03..e5b75f0f5 100755
--- a/youtube_dl/YoutubeDL.py
+++ b/youtube_dl/YoutubeDL.py
@@ -1798,7 +1798,7 @@ class YoutubeDL(object):
             else:
                 res = '%sp' % format['height']
         elif format.get('width') is not None:
-            res = '?x%d' % format['width']
+            res = '%dx?' % format['width']
         else:
             res = default
         return res