--- a/mercurial/help.py	Wed Dec 05 15:37:03 2018 -0800
+++ b/mercurial/help.py	Wed Dec 19 09:20:32 2018 -0800
@@ -160,7 +160,7 @@
         if shortopt:
             so = '-' + shortopt
         lo = '--' + longopt
-        if isinstance(default, bool):
+        if default is True:
             lo = '--[no-]' + longopt
 
         if isinstance(default, fancyopts.customopt):