We study architectural constraints for component systems in order to be able to guarantee safety-properties. Representing safety-properties, we investigate deadlock-freedom. We present a compositional and hence polynomial time condition for deadlock-freedom for a class of component-systems whose architecture is tree-like. The architectural constraints that are developed can be understood as a design pattern that helps to construct systems satisfying safety-properties on the one hand. On the other hand, they might help to draw attention to potentially critical situations in a design. To model component-systems we use the formalism of interaction systems as proposed by Sifakis et al. The ideas can be transferred to other formal models where subsystems are cooperating via synchronous communication.