In the vicinity of the phase‐matching angle of second‐order nonlinear optical crystals, the fundamental light wave experiences an intensity‐dependent phase shift which is connected with the effective attenuation due to second‐harmonic generation. It is demonstrated that in the limit of weak pump depletion, the Kramers–Kronig relations can be used to derive a simple analytical expression for the phase shift as a function of the phase‐mismatch angle. For certain mismatch angles, a large phase shift occurs without any attenuation. ©1995 American Institute of Physics.