--- a/mercurial/ui.py	Tue May 17 00:08:51 2011 +0200
+++ b/mercurial/ui.py	Tue May 17 00:17:52 2011 +0200
@@ -82,10 +82,12 @@
                       'traceback', 'verbose'):
                 if k in cfg['ui']:
                     del cfg['ui'][k]
+            for k, v in cfg.items('defaults'):
+                del cfg['defaults'][k]
+        # Don't remove aliases from the configuration if in the exceptionlist
+        if self.plain('alias'):
             for k, v in cfg.items('alias'):
                 del cfg['alias'][k]
-            for k, v in cfg.items('defaults'):
-                del cfg['defaults'][k]
 
         if trusted:
             self._tcfg.update(cfg)