The Cauchy problem for the dissipative wave equation \[ u_{tt} - \Delta u + u | u |^ p = 0, \quad t > 0, \quad x \in \mathbb{R}^ d \] with fast oscillating initial functions is considered. The problem is a passage of the fast oscillating wave through a focal point, where the wave amplitude is increasing that is predicted by the geometric optics method. The main result is as follows: The oscillations which may be present in the initial data do not survive a passage through the focus, if \((d-1)p \geq 2\).