It is well known that harmonic convolution of two normalized right halfplane mappings is convex in the direction of the real axis, provided the convolution function is locally univalent and sense-preserving in E = {z : |z| < 1}. Further, it is also known that the condition of local univalence and sense-preserving in E on the convolution function can be dropped when one of the convoluting functions is the standard right half-plane mapping with dilatation −z and other is the right halfplane mapping with dilatation e iθ z n , n = 1, 2, θ ∈ R. This result does not hold for n = 3, 4, 5, . . . . In this paper, we generalize this result by taking the dilatation of one of the right half-plane mappings as e iθ z n ( n ∈ N, θ ∈ R) and that of the other as (a − z)/(1 − az), a ∈ (−1, 1). We shall prove that our result holds true for all n ∈ N, provided the real constant a is restricted in the interval [(n − 2)/(n + 2), 1). The range of the real constant a is shown to be sharp.