Previous research has shown that while hearer-new unique definites are felicitous on their own, hearer-new names and incomplete definites are typically infelicitous (Sommers 1982; Roberts 2003). This paper presents two new observations regarding how appositives interact with these referring expressions. First, the infelicity of both hearer-new names and incomplete definites can be ameliorated by appositives that, pre-theoretically, clarify the reference of their anchor. Second, hearer-new incomplete definites are more constrained than names in terms of which appositives can effectively clarify their reference. I account for these observations by assuming that definites—but not names—conventionally encode uniqueness. These semantics are integrated into the system of Beaver and Coppock (2015). In this system, appositives disambiguate the values of indices attached to referring expressions, in some cases circumventing a pragmatic principle that adjudicates between competing logical forms.