This working paper documents a development of the standard Global Trade Analysis Project (GTAP) model to improve the way agricultural land supply is represented in the model and to make it more useful for Life Cycle Assessment (LCA) of products. The usefulness of the modifications is demonstrated by analysing changes in global wheat supply and consequences for agricultural land use caused by an increase in US household demand for wheat. We find that the impacts of the modifications are small in terms of the global wheat supply responses, but considerable in terms of land use changes. We therefore conclude that improving the way agricultural land supply is represented in the model is crucial whenever land use changes are of interest, whereas the standard GTAP model is a reasonable approximation in analyses that do not focus on agricultural land resources.