When complex systems are constructed from simplercomponents it is important to know how properties of thecomponents behave under composition. In this article, wepresent various compositionality results for security properties.In particular, we introduce a novel security propertyand show that this property is, in general, composable althoughit is weaker than forward correctability. Moreover,we demonstrate that certain nontrivial security propertiesemerge under composition and illustrate how this fact canbe exploited. All compositionality results that we presentare verified with the help of a single, quite powerful lemma.Basing on this lemma, we also re-prove several alreadyknown compositionality results with the objective to unifythese results. As a side effect, we obtain a classification ofknown compositionality results for security properties.