diff --git a/hgext/zeroconf/__init__.py b/hgext/zeroconf/__init__.py
--- a/hgext/zeroconf/__init__.py
+++ b/hgext/zeroconf/__init__.py
@@ -112,7 +112,7 @@ class hgwebzc(hgweb_mod.hgweb):
 class hgwebdirzc(hgwebdir_mod.hgwebdir):
     def run(self):
         for r, p in self.repos:
-            u = ui.ui(parentui=self.parentui)
+            u = self.parentui.copy()
             u.readconfig(os.path.join(p, '.hg', 'hgrc'))
             n = os.path.basename(r)
             publish(n, "hgweb", p, int(u.config("web", "port", 8000)))
diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -2677,13 +2677,13 @@ def serve(ui, repo, **opts):
         s = sshserver.sshserver(ui, repo)
         s.serve_forever()
 
-    parentui = repo and repo.baseui or ui
+    baseui = repo and repo.baseui or ui
     optlist = ("name templates style address port prefix ipv6"
                " accesslog errorlog webdir_conf certificate")
     for o in optlist.split():
         if opts[o]:
-            parentui.setconfig("web", o, str(opts[o]))
-            if (repo is not None) and (repo.ui != parentui):
+            baseui.setconfig("web", o, str(opts[o]))
+            if (repo is not None) and (repo.ui != baseui):
                 repo.ui.setconfig("web", o, str(opts[o]))
 
     if repo is None and not ui.config("web", "webdir_conf"):
@@ -2693,7 +2693,7 @@ def serve(ui, repo, **opts):
     class service:
         def init(self):
             util.set_signal_handler()
-            self.httpd = hgweb.server.create_server(parentui, repo)
+            self.httpd = hgweb.server.create_server(baseui, repo)
 
             if not ui.verbose: return
 
diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
--- a/mercurial/dispatch.py
+++ b/mercurial/dispatch.py
@@ -269,7 +269,7 @@ def _dispatch(ui, args):
         lui = ui
     if path:
         try:
-            lui = _ui.ui(parentui=ui)
+            lui = ui.copy()
             lui.readconfig(os.path.join(path, ".hg", "hgrc"))
         except IOError:
             pass
@@ -278,7 +278,7 @@ def _dispatch(ui, args):
     rpath = _earlygetopt(["-R", "--repository", "--repo"], args)
     if rpath:
         path = lui.expandpath(rpath[-1])
-        lui = _ui.ui(parentui=ui)
+        lui = ui.copy()
         lui.readconfig(os.path.join(path, ".hg", "hgrc"))
 
     extensions.loadall(lui)
diff --git a/mercurial/hgweb/hgwebdir_mod.py b/mercurial/hgweb/hgwebdir_mod.py
--- a/mercurial/hgweb/hgwebdir_mod.py
+++ b/mercurial/hgweb/hgwebdir_mod.py
@@ -203,7 +203,7 @@ class hgwebdir(object):
                     continue
                 name = name[len(subdir):]
 
-                u = ui.ui(parentui=self.parentui)
+                u = self.parentui.copy()
                 try:
                     u.readconfig(os.path.join(path, '.hg', 'hgrc'))
                 except Exception, e:
diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -13,7 +13,7 @@ import config, traceback, util, error
              '0':False, 'no':False, 'false':False, 'off':False}
 
 class ui(object):
-    def __init__(self, parentui=None):
+    def __init__(self, src=None):
         self.buffers = []
         self.quiet = self.verbose = self.debugflag = self.traceback = False
         self.interactive = self.report_untrusted = True
@@ -23,12 +23,12 @@ class ui(object):
         self.trusted_users = {}
         self.trusted_groups = {}
 
-        if parentui:
-            self.cdata = parentui.cdata.copy()
-            self.ucdata = parentui.ucdata.copy()
-            self.overlay = parentui.overlay.copy()
-            self.trusted_users = parentui.trusted_users.copy()
-            self.trusted_groups = parentui.trusted_groups.copy()
+        if src:
+            self.cdata = src.cdata.copy()
+            self.ucdata = src.ucdata.copy()
+            self.overlay = src.overlay.copy()
+            self.trusted_users = src.trusted_users.copy()
+            self.trusted_groups = src.trusted_groups.copy()
             self.fixconfig()
         else:
             # we always trust global config files
diff --git a/tests/test-trusted.py b/tests/test-trusted.py
--- a/tests/test-trusted.py
+++ b/tests/test-trusted.py
@@ -59,9 +59,8 @@ def testui(user='foo', group='bar', tuse
     print '# %s user, %s group%s' % (kind[user == cuser], kind[group == cgroup],
                                      trusted)
 
-    parentui = ui.ui()
-    parentui.setconfig('ui', 'debug', str(bool(debug)))
-    u = ui.ui(parentui=parentui)
+    u = ui.ui()
+    u.setconfig('ui', 'debug', str(bool(debug)))
     u.readconfig('.hg/hgrc')
     if silent:
         return u
@@ -146,7 +145,7 @@ print "# read trusted, untrusted, new ui
 u = ui.ui()
 u.setconfig('ui', 'debug', 'on')
 u.readconfig(filename)
-u2 = ui.ui(parentui=u)
+u2 = u.copy()
 def username(uid=None):
     return 'foo'
 util.username = username