This paper presents challenges and observations on creating a code-switching treebank based on ongoing annotation efforts of a Turkish-German spoken corpus following the Universal Dependencies annotation scheme. We present and discuss a number of issues that arise because of the need for consistent multilingual annotation within a single treebank, as well as the informal language which is where code-switching is observed most. Besides proposing solutions to these issues, our aim in this paper is to stimulate discussion and facilitate consistency over upcoming code-switching annotation projects.