Filament mass function (FMF) for various FDM masses at redshift z = 4. The suppression in the linear FDM power spectrum translates to a power suppression for filament masses. For filament masses M > 3 × 10⁹ h⁻¹ M_⊙, all considered FDM cases are indistinguishable from CDM and it is in this regime in which we sample the FMF in order to guarantee the same overall number density and thus same significance of interference effects measured in the correlation functions discussed in Sect. 3.