A system for mulling a plurality of fenestration assemblies in an opening includes a first fenestration assembly having a top surface and a first groove extending therein and a second fenestration assembly having a top surface and a second groove extending therein. A mull connector operatively connects the first fenestration assembly and second fenestration assembly together. A sealing cap is positioned on top of the mull connector and includes a first portion positioned on a first side of a line groove line defined by the first groove and the second groove, and a second portion positioned on the second opposite side of the line groove.