The vesicular adenosine triphosphatase (ATPase) acidifies intracellular compartments, including synaptic vesicles and secretory granules. A controversy about a second function of this ATPase in exocytosis has been fuelled by questions about multiple putative roles of acidification in the exocytic process. Now, Poëa-Guyon et al. (2013. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201303104) present new evidence that the vesicular ATPase performs separate acidification and exocytosis roles and propose a mechanism for how these two functions are causally linked.