diff --git a/mercurial/templatefilters.py b/mercurial/templatefilters.py
--- a/mercurial/templatefilters.py
+++ b/mercurial/templatefilters.py
@@ -234,7 +234,7 @@ def json(obj, paranoid=True):
     elif isinstance(obj, bytes):
         return '"%s"' % encoding.jsonescape(obj, paranoid=paranoid)
     elif util.safehasattr(obj, 'keys'):
-        out = ['%s: %s' % (json(k), json(v))
+        out = ['"%s": %s' % (encoding.jsonescape(k, paranoid=paranoid), json(v))
                for k, v in sorted(obj.iteritems())]
         return '{' + ', '.join(out) + '}'
     elif util.safehasattr(obj, '__iter__'):