This paper presents a revised linear stability analysis for the onset of natural convection in a horizontal nanofluid layer. The employed model incorporates the effects of Brownian motion and thermophoresis. It is now assumed that the value of the temperature can be imposed on the boundaries, but the nanoparticle fraction adjusts so that the nanoparticle flux is zero on the boundaries. It is shown that, with the new boundary conditions, oscillatory convection can no longer occur. The pertinent dimensionless nanofluid parameters have been rescaled. The effect of the nanoparticles on non-oscillatory convection is destabilizing. (C) 2014 Elsevier Ltd. All rights reserved.