diff --git a/mercurial/fancyopts.py b/mercurial/fancyopts.py
--- a/mercurial/fancyopts.py
+++ b/mercurial/fancyopts.py
@@ -77,7 +77,7 @@ def fancyopts(args, options, state, gnu=
         # copy defaults to state
         if isinstance(default, list):
             state[name] = default[:]
-        elif getattr(default, '__call__', False):
+        elif callable(default):
             state[name] = None
         else:
             state[name] = default