The tedious process of corrective and perfective maintenance is often automated thanks to rewriting rules using tools such as Spoon or Coccinelle. These tools consider rules as black-boxes, and compose multiple rules by giving the output of a given rewriting as input to the next one. It is up to the developer to identify the right order (if it exists) among all the different rules. In this paper, we define a formal model compatible with the black-box assumption that reifies the modifications (∆s) made by each rule. Leveraging these ∆s, we propose a way to safely compose multiple rules when applied to the same program by (i) ensuring the isolated application of the different rules and (ii) yield unexpected behaviors that were silently ignored before. We assess this approach by applying rewriting rules used to fix anti-patterns existing in Android applications to external pieces of software available on GitHub.