We derived a formula for calculation of the spectral phase of ultrashort pulses propagating through aberrated stretchers. Our approach is based on Seidel aberration theory. The dependence of spectral phase dispersion terms and residual angular dispersion on the individual Seidel aberration coefficients is found. As an example, the spectral phase deviation and the residual angular dispersion of an ultrashort pulse for the Martinez/Banks stretcher using spherical optics is calculated.