This article investigates a series of additions made to JRL Gaster MS 2037, a newly identified copy of Peter of Poitier‘s Compendium historiae in genealogia Christi. Following a detailed description and dating of the manuscript, it investigates two sets of additions to the roll in depth. It establishes that the first motive behind the inclusion of such additions was educative – serving to extend the historic information given in the Compendium, while the second motive was devotional – elevating the status of the Virgin Mary through the enhancement of her genealogical record. Given the fact that the manuscript was produced in the mid-fifteenth century, this focus on the Virgin likely had a polemic purpose, situating the manuscript in the context of debates over the Immaculate Conception, and using Alexander Nequams Expositio super Cantica canticorumto this end. In identifying the sources used, as well as the limits on the compiler imposed by the physical form of the roll, this examination of Gaster MS 2037 offers an insight into the later reception of this popular text.