By now it is well-known that most (if not all) globular clusters harbour at least two generations of stars. This fact is observed in, for instance, anticorrelations of [Na/Fe]-[O/Fe] and [Mg/Fe]-[Al/Fe]. These correlations are believed to be caused by self-enrichment from an earlier generation of stars. However, the nature of these first-generation polluters is still a matter of debate, being AGB stars, Very Massive Fast Rotators or something else entirely. In cases where isotopic mixtures can be measured, additional constraints can be put on the first generation cluster stars and on the nucleosynthesis history of the cluster. Here we present results on Mg-isotopic ratios in giant stars in the metal-rich globular cluster 47 Tucanae. This is the most metal-rich cluster in which such an analysis has been performed to date and will provide an important test of nucleosynthesis in a high-metallicity environment.