A two-parameter corresponding-states correlation, based upon the Redlich-Kwong equation, is proposed for the second virial coefficient at relatively high temperature (reduced temperature above 0.8). This remarkably simple correlation suggests an improvement to the venerable Redlich-Kwong equation of state, gives guidance for the high-temperature extrapolation of a-functions, and provides an independent tool to evaluate theoretical and empirical correlations for the second virial coefficient.