1 files changed, 3 insertions, 0 deletions
diff --git a/docs/modules/password_auth_provider_callbacks.md b/docs/modules/password_auth_provider_callbacks.md
index 8275f7ebdc..d66ac7df31 100644
--- a/docs/modules/password_auth_provider_callbacks.md
+++ b/docs/modules/password_auth_provider_callbacks.md
@@ -46,6 +46,9 @@ instead.
 
 If the authentication is unsuccessful, the module must return `None`.
 
+Note that the user is not automatically registered, the `register_user(..)` method of
+the [module API](writing_a_module.html) can be used to lazily create users.
+
 If multiple modules register an auth checker for the same login type but with different
 fields, Synapse will refuse to start.