Autonomous agents optimize the reward function we give them. What they don't know is how hard it is for us to design a reward function that actually captures what we want. When designing the reward, we might think of some specific scenarios (driving on clean roads), and make sure that the reward will lead to the right behavior in \emph{those} scenarios. Inevitably, agents encounter \emph{new} scenarios (snowy roads), and optimizing the reward can lead to undesired behavior (driving too fast). Our insight in this work is that reward functions are merely \emph{observations} about what the designer \emph{actually} wants, and that they should be interpreted in the context in which they were designed. We introduce \emph{Inverse Reward Design} (IRD) as the problem of inferring the true reward based on the designed reward and the training MDP. We introduce approximate methods for solving IRD problems, and use their solution to plan risk-averse behavior in test MDPs. Empirical results suggest that this approach takes a step towards alleviating negative side effects and preventing reward hacking.