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Until recently, published documentation of the Berber varieties of the Nefusa Mountains in Libya was limited to the area around Jadu. Newer data on the varieties of Yefren and Wazzin makes it clear that “Nefusi” is a paraphyletic areal unit, whose history can be reconstructed in the light of comparative data from other varieties: peripheral Nefusi varieties belong unambiguously to the Zenati subgroup of Berber, but central Nefusi is a mixed variety resulting from incomplete convergence of a Ghadames-like variety towards a formerly more widespread Zenati lingua franca. This case study demonstrates that, while the linguistic history of Berber does not fit a strict tree model, it can nevertheless be understood in terms of a mixed tree model taking into account family-internal diffusion.