The definition of the Ravenscar Tasking Profile for Ada 95 provides a definition of a tasking runtime system with deterministic behaviour and low enough complexity to permit a formal description and verification of the model. A complete run-time system is being modeled using the real-time model checker UPPAAL, and this work describes the handling of delay until. Since scheduling is not yet modelled a simple non-preemptive scheduler has been used when verifying the delay queue.