Product line models are used to drive the generation of requirements for single systems in the product line. They are difficult to validate because they are large and complex. By modelling variability and dependency between requirements using propositional connectives, a logical expression can be developed for the model. Validation of the selection of requirements from the model can be achieved by satisfying the logical expression. This approach can be used to validate the model as a whole. A detailed worked example is presented, and the computational aspects of the approach are discussed.