diff -r 16a46003b50c -r 06c8b58647b9 mercurial/formatter.py
--- a/mercurial/formatter.py	Wed Oct 01 03:42:00 2014 +0200
+++ b/mercurial/formatter.py	Thu Oct 02 23:20:59 2014 +0900
@@ -91,6 +91,10 @@
 def _jsonifyobj(v):
     if isinstance(v, tuple):
         return '[' + ', '.join(_jsonifyobj(e) for e in v) + ']'
+    elif v is True:
+        return 'true'
+    elif v is False:
+        return 'false'
     elif isinstance(v, (int, float)):
         return str(v)
     else: