diff --git a/mwclient/client.py b/mwclient/client.py
index a255afb31ea606a7e037986cae25af7b260442d8..f462982fded418e0deb04154de53b80a6d6c1a68 100644
--- a/mwclient/client.py
+++ b/mwclient/client.py
@@ -379,7 +379,7 @@ class Site(object):
 			predata['session_key'] = session_key 
 		
 		if file is None:
-			postdata = predata
+			postdata = self._query_string(predata)
 		else:			
 			if type(file) is str:
 				file_size = len(file)