In a course on sustainable design strategies, students explore different notions of what it means to be sustainable and what that, in turn, implies for how one should design products. Many of the philosophical notions that have been proposed (such as Circular Economy, Cradle 2 Cradle, and Biomimicry), and the tools and methods that accompany them, still have substantial shortcomings. As a teacher, I could lecture about those shortcomings and talk about many cases, each with their own particular hurdles, but I deem it more educational for students to bump into, or trip over such hurdles themselves. Enter the notion of Annotated Failure. I ask students to try a sustainable design method until they get stuck, and to submit an annotated version of their design process as a course deliverable. If they reflect deeply on why they got stuck, they will see that often the design method failed them. Still, students often feel they failed themselves, even after finishing the course. In a certain sense, this may mean I have failed to adequately implement Annotated Failure as a teaching strategy. This paper serves therefore as an annotated reflection.