We present homogeneous nucleation rates in the binary mixture n-nonane/methane in the supercritical regime, measured in a new pulse expansion tube at pressures up to 40 bar, at a temperature of 240 K. It is shown that both n-nonane and methane are present in the critical cluster. The critical supersaturation of n-nonane decreases from 30 at 10 bar, down to 6 at 40 bar total pressure.