Aborting a transaction that began while an index build is in progress may invoke registered changes in the RecoveryUnit to rollback changes to the temporary tables used by the index build. In the event of a replica set step down, the index build may be cleaned up, along with the associated IndexBuildInterceptor and the temporary tables, before the abort procedure is completed for the transaction. This may result in the rollback handler in the RecoveryUnit accessing the internal state of an IndexBuildInterceptor that is no longer available. A potential scenario, which requires SERVER-42824 to be implemented , is described in SERVER-42621.