--- a/mercurial/ui.py	Wed Mar 19 01:59:15 2014 +0100
+++ b/mercurial/ui.py	Wed Mar 19 02:45:04 2014 +0100
@@ -157,9 +157,9 @@
         self._tcfg.restore(data[1])
         self._ucfg.restore(data[2])
 
-    def setconfig(self, section, name, value):
+    def setconfig(self, section, name, value, source=''):
         for cfg in (self._ocfg, self._tcfg, self._ucfg):
-            cfg.set(section, name, value)
+            cfg.set(section, name, value, source)
         self.fixconfig(section=section)
 
     def _data(self, untrusted):