Boson bunching is among the most remarkable features of quantum physics. A celebrated example in optics is the Hong–Ou–Mandel effect, where the bunching of two photons arises from a destructive quantum interference between the trajectories where they both either cross a beamsplitter or are reflected. This effect takes its roots in the indistinguishability of identical photons. Hence, it is generally admitted—and experimentally verified—that bunching vanishes as soon as photons can be distinguished, for example, when they occupy distinct time bins or have different polarizations. Here we disprove this alleged straightforward link between indistinguishability and bunching by exploiting a recent finding in the theory of matrix permanents. We exhibit a family of optical circuits such that the bunching of photons into two modes can be substantially boosted by making them partially distinguishable via an appropriate polarization pattern. This boosting effect is already visible in a seven-photon interferometric process, making the observation of this phenomenon within reach of current photonic technology. This unexpected behaviour questions our understanding of multiparticle interference in the grey zone between indistinguishable bosons and classical particles. A common belief about boson bunching—fully indistinguishable bosons exhibit the utmost bunching—is theoretically disproved with seven photons of distinct polarization in a seven-mode interferometric process. Enhanced bunching could thus be observed with partially distinguishable photons.