Robot sensors are usually subject to error. Since in many practical scenarios a probabilistic error model is not available, sen- sor readings are often dealt with in a hard-coded, heuristic fashion. In this paper, we propose a logic to address the problem from a KR perspective. In this logic the epistemic effect of sensing actions is deferred to so-called fusion actions, which may resolve discrepan- cies and inconsistencies of recent sensing results. Moreover, a local closed world assumption can be applied dynamically. When needed, this assumption can be revoked and fusions can be undone using a form of forgetting.