An error in a previous publication on the interpretation of static steam dryness versus flowing steam quality in the coding of the simulator GWELL is corrected here. GWELL does in fact have the correct derivation of flowing steam quality in its CO2 subroutine. The mathematics behind this derivation is briefly reviewed in this corrigendum. WELLSIM also passes the energy test mentioned in that publication. (C) 2015 Elsevier Ltd. All rights reserved.