diff -r a14e2e7f7d1f -r 77e666f943a6 mercurial/ui.py
--- a/mercurial/ui.py	Tue Jun 27 02:06:15 2017 +0200
+++ b/mercurial/ui.py	Wed Jun 28 13:50:20 2017 +0200
@@ -455,6 +455,8 @@
             if default is _unset:
                 if item is None:
                     value = default
+                elif callable(item.default):
+                    value = item.default()
                 else:
                     value = item.default
             elif item is not None: