Test of lepton flavour universality with b $\to$ s$\ell \ell$ decays at the LHCb experiment

Current measurements of the LHCb experiment hint to deviations from Standard Model predictions in tests of lepton flavour universality. An example for this is the measurement of R${}_{K^{\ast 0}}$, the ratio of the branching fractions of the decays B${}^0$$\to$ K${}^{\ast 0}$${\mu }^{+}{\mu }^{-}$ and B${}^0$$\to$ K${}^{\ast 0}$$e^{+}{e}^{-}$. This measurement was performed with the a dataset corresponding to an integrated luminosity of 3 fb. For conclusive results the measurements have to include the extended LHCb dataset. In this talk the updated measurement of R${}_{K^{\ast 0}}$, which is currently under preparation, is presented.