diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -471,12 +471,16 @@ class ui(object):
         return value
 
     def _config(self, section, name, default=_unset, untrusted=False):
-        value = default
+        value = itemdefault = default
         item = self._knownconfig.get(section, {}).get(name)
         alternates = [(section, name)]
 
         if item is not None:
             alternates.extend(item.alias)
+            if callable(item.default):
+                itemdefault = item.default()
+            else:
+                itemdefault = item.default
         else:
             msg = ("accessing unregistered config item: '%s.%s'")
             msg %= (section, name)
@@ -490,13 +494,12 @@ class ui(object):
                 msg = "config item requires an explicit default value: '%s.%s'"
                 msg %= (section, name)
                 self.develwarn(msg, 2, 'warn-config-default')
-            elif callable(item.default):
-                    value = item.default()
             else:
-                value = item.default
+                value = itemdefault
         elif (item is not None
-              and item.default is not configitems.dynamicdefault):
-            msg = ("specifying a default value for a registered "
+              and item.default is not configitems.dynamicdefault
+              and default != itemdefault):
+            msg = ("specifying a mismatched default value for a registered "
                    "config item: '%s.%s' '%s'")
             msg %= (section, name, default)
             self.develwarn(msg, 2, 'warn-config-default')
diff --git a/tests/test-devel-warnings.t b/tests/test-devel-warnings.t
--- a/tests/test-devel-warnings.t
+++ b/tests/test-devel-warnings.t
@@ -352,17 +352,21 @@ Test warning on config option access and
   > 
   > configitem('test', 'some', default='foo')
   > configitem('test', 'dynamic', default=configitems.dynamicdefault)
+  > configitem('test', 'callable', default=list)
   > # overwrite a core config
   > configitem('ui', 'quiet', default=False)
   > configitem('ui', 'interactive', default=None)
   > 
   > @command(b'buggyconfig')
   > def cmdbuggyconfig(ui, repo):
-  >     repo.ui.config('ui', 'quiet', False)
-  >     repo.ui.config('ui', 'interactive', None)
+  >     repo.ui.config('ui', 'quiet', True)
+  >     repo.ui.config('ui', 'interactive', False)
+  >     repo.ui.config('test', 'some', 'bar')
   >     repo.ui.config('test', 'some', 'foo')
   >     repo.ui.config('test', 'dynamic', 'some-required-default')
   >     repo.ui.config('test', 'dynamic')
+  >     repo.ui.config('test', 'callable', [])
+  >     repo.ui.config('test', 'callable', 'foo')
   >     repo.ui.config('test', 'unregistered')
   >     repo.ui.config('unregistered', 'unregistered')
   > EOF
@@ -370,10 +374,11 @@ Test warning on config option access and
   $ hg --config "extensions.buggyconfig=${TESTTMP}/buggyconfig.py" buggyconfig
   devel-warn: extension 'buggyconfig' overwrite config item 'ui.interactive' at: */mercurial/extensions.py:* (_loadextra) (glob)
   devel-warn: extension 'buggyconfig' overwrite config item 'ui.quiet' at: */mercurial/extensions.py:* (_loadextra) (glob)
-  devel-warn: specifying a default value for a registered config item: 'ui.quiet' 'False' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
-  devel-warn: specifying a default value for a registered config item: 'ui.interactive' 'None' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
-  devel-warn: specifying a default value for a registered config item: 'test.some' 'foo' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
+  devel-warn: specifying a mismatched default value for a registered config item: 'ui.quiet' 'True' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
+  devel-warn: specifying a mismatched default value for a registered config item: 'ui.interactive' 'False' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
+  devel-warn: specifying a mismatched default value for a registered config item: 'test.some' 'bar' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
   devel-warn: config item requires an explicit default value: 'test.dynamic' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
+  devel-warn: specifying a mismatched default value for a registered config item: 'test.callable' 'foo' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
   devel-warn: accessing unregistered config item: 'test.unregistered' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
   devel-warn: accessing unregistered config item: 'unregistered.unregistered' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)