  We prove a general congruence result for bisimilarity in higher-order
languages, which generalises previous work to languages specified by a labelled
transition system in which programs may occur as labels, and which may rely on
operations on terms other than capture-avoiding substitution. This is typically
the case for PCF, $\lambda$-calculus with delimited continuations, and
early-style bisimilarity in higher-order process calculi.
