The effect of the Gribov horizon in Euclidean SU(2) gauge theory is studied. Gauge fields on the Gribov horizon yield zero modes of ghosts and antighosts. We show these zero modes can produce additional ghost interactions, and the Landau gauge changes to a nonlinear gauge effectively. In the infrared limit, however, the Landau gauge is recovered, and ghost zero modes may appear again. We show ghost condensation happens in the nonlinear gauge, and the zero mode repetition is avoided.