--- a/app.go	Sat Apr 29 10:51:45 2017 +0200
+++ b/app.go	Sat Apr 29 12:16:16 2017 +0200
@@ -68,7 +68,7 @@
 	}
 
 	var app registerApp
-	if err := mc.apiCall("apps", rest.Post, params, nil, &app); err != nil {
+	if err := mc.apiCall("apps", rest.Post, params, nil, nil, &app); err != nil {
 		return nil, err
 	}