Negotiations to bring peace to Syria have taken place in an environment of increasing attention being paid to inclusivity of civil society actors in peace negotiations. In 2014, Lakhdar Brahimi could still get away with marginal civil society inclusion in the Geneva II negotiations. In 2016, Staffan de Mistura created an innovative mechanism for civil society inclusion providing them a physical space at the Palais des Nations where proximity talks are being held between the opposition and the government delegations. The question is what accounted for this normative change when the mandating organization remained the same (the UN) and the parties’ delegations are largely identical. The paper explores the diffusion of the inclusivity norm and assesses whether it was rather caused by outside pressure or internal dynamics of the peace process. Outside pressure encompasses norms advocates calling for more inclusivity by referring to the increasing amount of policy papers and academic publications underlining its importance. Internal dynamics relate to the normative socialization of the mediator or strategic considerations to confer the process with more legitimacy. While there is obviously not an either-or answer, the paper seeks to shed light on how normative change comes about in mediation processes.