diff -r a71578ec6257 -r 7e20b705da5b tests/test-config.t
--- a/tests/test-config.t	Sun Oct 27 12:36:52 2019 +0900
+++ b/tests/test-config.t	Sun Oct 27 12:49:09 2019 +0900
@@ -122,7 +122,7 @@
   ]
   $ hg config --config auth.cookiefile= auth -T'json(defaultvalue)'
   [
-   {"defaultvalue": ""}
+   {"defaultvalue": null}
   ]
   $ hg config --config auth.cookiefile= auth -T'{defaultvalue}\n'