We study the problem of verifying the robustness of concurrent programs against a C11-style memory model that includes relaxed accesses and release/acquire accesses and fences, and show that this verification problem can be reduced to a standard reachability problem under sequential consistency. We further observe that existing robustness notions do not allow the verification of programs that use speculative reads as in the sequence lock mechanism, and introduce a novel “observational robustness” property that fills this gap. In turn, we show how to soundly check for observational robustness. We have implemented our method and applied it to several challenging concurrent algorithms, demonstrating the applicability of our approach. To the best of our knowledge, this is the first method for verifying robustness against a programming language concurrency model that includes relaxed accesses and release/acquire fences.