On the basis of a simple example, it is shown that unrealistic ''numerical'' boundary layers can develop along solid boundaries in models using a certain type of staggered computational grid. In this particular case the artifact can be ascribed to the discretization of the Coriolis term along the boundary combined with the inadequacy of the boundary condition. As a consequence of that error, the solution of a three-dimensional numerical model is found to converge toward an incorrect steady state (the residual mean flow does not vanish as it should). A straghtforward correction, called the ''wet-points-only'' method, is proposed. The procedure consists of eliminating the boundary points from the evaluation of the Coriolis term. The wet-point-only method is shown to also affect the results obtained with a two-dimensional (vertically integrated) model. In this case, however, the implementation of the procedure usually downgrades rather than improves the numerical solution. For schemes wherein the velocity components are not calculated at the same locations, care must be taken in the evaluation of any term that couples the two components of the momentum equation.