  We investigate whether the $2.6\sigma$ deviation from lepton flavour
universality in $B^+\to K^+\ell^+\ell^-$ decays recently observed at the LHCb
experiment can be explained in minimal composite Higgs models. We show that a
visible departure from universality is indeed possible if left-handed muons
have a sizable degree of compositeness. Constraints from $Z$-pole observables
are avoided by a custodial protection of the muon coupling. The deficit in the
invisible $Z$ width at LEP is explained in the same region of parameters.
