Creating a requirement specification for modify a production system design is difficult. When modifying a production system the methodologies utilized span from full methodical and rational way to a trial and error approach. Often when modifying a production system there is more or less no requirement specification done in advance at all. This is due to a number of causes e.g. time pressure and lack of knowledge in the specific area and strong focus on a quick solution. Low understanding of the effects of an absent requirement specification and unclear relations to how the outcome of the production system modification will be affected by the identified requirements is often why the requirement specification is neglected. To visualize the need and impact of the requirements specification on the final system it would be beneficial to simulate the requirement specification. A suggested technique is to create a model where verification of the requirement specification could be done. This paper demonstrates the requirement complexity from a SME perspective when implementing a new robot module in a production system at Componenta Främmestad, Sweden. The paper also elaborates and discusses a possible approach for deciding requirements for a production system design verification model.