In this article, we explore the impact of self-serving biases on the demand for redis- tribution. To do so, we run an experiment in which participants vote on redistribution after having earned income in a real effort task. Participants are randomly assigned to either a hard or easy task. However, because we withhold the information about the relative task difficulty there is ambiguity as to whether success or failure should be at- tributed to internal or external factor. Our results confirm and expand previous findings on the self-serving bias: successful participants ask for less redistribution because they are more likely to attribute their success to their effort rather than luck. The innovative contribution of our work consists in mimicking political debates, in which participants have very limited information on the exogenous factors at stake. In this regard, our findings show that the impact of the self-serving bias is much more far-reaching than what is commonly hold. We also discuss the implications of the self-serving bias for the institutional framework.