It is a well-known fact that for every k-safe Petri net, i.e. a Petri net in which no place contains more than k ∈ ℕ tokens under any reachable marking, there is a 1-safe Petri net with the same interleaving behaviour. Indeed these types of Petri nets generate regular languages. In this paper, we show that this equivalence of k-safe and 1-safe Petri nets holds also for their pomset languages, a true-concurrency semantics.