diff --git a/docs/config.md b/docs/config.md
index 1ff8a7cfb3..01a869a837 100644
--- a/docs/config.md
+++ b/docs/config.md
@@ -80,6 +80,7 @@ For a good example, see https://riot.im/develop/config.json.
 1. `defaultCountryCode`: The ISO 3166 alpha2 country code to use when showing
    country selectors, like the phone number input on the registration page.
    Defaults to `GB` if the given code is unknown or not provided.
+1. `settingDefaults`:  Defaults for settings that support the `config` level, as an object mapping setting name to value (note that the "theme" setting is special cased to the `default_theme` in the config file).
 1. `disable_custom_urls`: disallow the user to change the
    default homeserver when signing up or logging in.