diff --git a/src/interactive-auth.js b/src/interactive-auth.js
index dddae0f5e..c295a13ec 100644
--- a/src/interactive-auth.js
+++ b/src/interactive-auth.js
@@ -56,7 +56,13 @@ const MSISDN_STAGE_TYPE = "m.login.msisdn";
  *     called when the status of the UI auth changes, ie. when the state of
  *     an auth stage changes of when the auth flow moves to a new stage.
  *     The arguments are: the login type (eg m.login.password); and an object
- *     specific to the login type. These are:
+ *     which is either an error or an informational object specific to the
+ *     login type. If the 'errcode' key is defined, the object is an error,
+ *     and has keys:
+ *         errcode: string, the textual error code, eg. M_UNKNOWN
+ *         error: string, human readable string describing the error
+ *
+ *     The login type specific objects are as follows:
  *         m.login.email.identity:
  *          * emailSid: string, the sid of the active email auth session
  *