Existing accounts of social insurance tend to treat social risks as given and ask whether it is justified for the state to deal with these risks for its citizens. They ignore that many common risks are in fact imposed on citizens as a byproduct of the institutional choices of the society, which call for justification in the first place. In this paper, I use the Scanlonian contractualist framework to develop an account of just social risk imposition which implies a demand (...) for fair risk sharing by all members of a society. In particular, I defend a compensation principle which requires that compensation be paid to victims of risk materialisation. This duty of paying should be shared by all those who benefit from the imposition of the relevant risk. I suggest that this provides a case for social insurance as a way of fairly sharing the burden of social risks. (shrink)