In evaluating the conventional weak-turbulence equations for ion-sound turbulence somewhat more carefully, it is found that the theoretical value of the turbulent energy W = ⟨2⟩/4πnTe is consistent with observations on collisionless shock waves. However, calculating the anomalous resistivity η using this value of W, η turns out to be too large, regardless of whether simple quasi-linear theory or the strong-trapping theory of Dupree is used.