diff --git a/embed_video/templatetags/embed_video_tags.py b/embed_video/templatetags/embed_video_tags.py
index 983ddb5..91c0b6d 100644
--- a/embed_video/templatetags/embed_video_tags.py
+++ b/embed_video/templatetags/embed_video_tags.py
@@ -48,7 +48,7 @@ class VideoNode(Node):
     error_msg = 'Syntax error. Expected: ``{% video URL ... %}``'
     default_size = 'small'
 
-    re_size = re.compile('(?P<width>\w+[%]?)x(?P<height>\w+[%]?)')
+    re_size = re.compile('(?P<width>\d+[%]?)x(?P<height>\d+[%]?)')
 
     def __init__(self, parser, token):
         self.size = None