A simple approximation within the framework of the hybrid methods for the calculation of the electronic structure of solids is presented. By considering only the diagonal elements of the matrix of the perturbation operator (Hartree-Fock exchange minus semilocal exchange) calculated in the basis of the semilocal orbitals, the computational time is drastically reduced, while keeping very well in most studied cases the accuracy of the results obtained with hybrid functionals when applied without any approximations.