diff --git a/youtube_dl/YoutubeDL.py b/youtube_dl/YoutubeDL.py
index fcb8dd19c..523eba3c1 100644
--- a/youtube_dl/YoutubeDL.py
+++ b/youtube_dl/YoutubeDL.py
@@ -416,9 +416,9 @@ class YoutubeDL(object):
                 if template_dict.get('width') and template_dict.get('height'):
                     template_dict['resolution'] = '%dx%d' % (template_dict['width'], template_dict['height'])
                 elif template_dict.get('height'):
-                    res = '%sp' % template_dict['height']
+                    template_dict['resolution'] = '%sp' % template_dict['height']
                 elif template_dict.get('width'):
-                    res = '?x%d' % template_dict['width']
+                    template_dict['resolution'] = '?x%d' % template_dict['width']
 
             sanitize = lambda k, v: sanitize_filename(
                 compat_str(v),