  We study the constraints of supersymmetry on flavour in recently proposed
models of F-theory GUTs. We relate the topologically twisted theory to the
canonical presentation of eight-dimensional super Yang-Mills and provide a
dictionary between the two. We describe the constraints on Yukawa couplings
implied by holomorphy of the superpotential in the effective 4-dimensional
supergravity theory, including the scaling with \alpha_{GUT}. Taking D-terms
into account we solve explicitly to second order for wavefunctions and Yukawas
due to metric and flux perturbations and find a rank-one Yukawa matrix with no
subleading corrections.
