It has recently been suggested that the reaction between vibrationally excited H-2(nu = 1) and O(P-3) atoms may be an important source of OH in the upper mesosphere. Here, we report accurate quantum calculations of rate coefficients for the O(P-3) + H-2(nu = 1) reaction and show that the proposed mechanism is not an important source of OH in the mesosphere. Our calculation employs chemically accurate potential energy surfaces for the O + H-2 system and quantum mechanical method for the calculation of the relevant cross sections and rate coefficients.