diff --git a/clientapi/routing/register.go b/clientapi/routing/register.go
index cfd7f64eb..9f90083bc 100644
--- a/clientapi/routing/register.go
+++ b/clientapi/routing/register.go
@@ -627,6 +627,10 @@ func handleRegistrationFlow(
 		// Add Dummy to the list of completed registration stages
 		AddCompletedSessionStage(sessionID, authtypes.LoginTypeDummy)
 
+	case "":
+		// An empty auth type means that we want to fetch the available
+		// flows. It can also mean that we want to register as an appservice
+		// but that is handed above.
 	default:
 		return util.JSONResponse{
 			Code: http.StatusNotImplemented,