RGBD cameras capturing color and depth information are highly promising for various industrial, consumer and creative applications. Among others, these applications are segmentation, gesture control or deep compositing. Depth maps captured with Time-of-Flight sensors, as a potential alternative to vision-based approaches, still suffer from low depth resolution. Various algorithms are available for RGB-guided depth upscaling but they also introduce filtering artifacts like depth bleeding or texture copying. We propose a novel superpixel-based upscaling algorithm, which employs an iterative superpixel clustering strategy to achieve improved boundary reproduction at depth discontinuities without aforementioned artifacts. Concluding, a rich ground-truth-based evaluation validates that our upscaling method is superior compared to competing state-of-the-art algorithms with respect to depth jump reproduction. Reference material is collected from a real RGBD camera as well as the Middlebury 2005 and 2014 data sets. The effectiveness of our method is also confirmed by usage in a depth-jump-critical computational imaging use case.