Assertions are the centre of gravity in social epistemology. They are the vehicles we use to exchange information within scientific groups and society as a whole. It is therefore essential to determine under which conditions we are permitted to make an assertion. In this paper we argue and provide empirical evidence for the view that the norm of assertion is justified belief: truth or even knowledge are not required. Our results challenge the knowledge account advocated by, e.g. Williamson (1996), in general, and more specifically, put into question several studies conducted by Turri (2013, 2016) that support a knowledge norm of assertion. Instead, the justified belief account championed by, e.g. Douven (2006), seems to prevail