The structural properties of the hexagonal multiferroic h-HoMnO3 under high pressure have been explored using synchrotron x-ray diffraction and x-ray absorption spectroscopy in diamond anvil cells. The structure was found to undergo a pressure-induced phase transition at ∼24 GPa to a rhombohedrally distorted superstructure, which is isostructural to the oxygen-loaded h-RMnO3+δ (R=Y,Dy,Ho,Er; δ≈0.28) phases found in the same systems. The driving force behind the phase transition is the highly compressible ab plane which facilitates a gradual charge disproportionation of Mn(III) with pressure. We speculate this stabilizes the spin-liquid phase due to ferromagnetic coupling between neighboring Mn(II)/Mn(IV) and Mn(III). In addition, we demonstrate that the structural behavior is highly susceptible to nonhydrostatic conditions and the choice of pressure medium should be carefully made.