In a data processing system, a method includes a first master initiating a transaction via a system interconnect to a target device. After initiating the transaction, a snoop request corresponding to the transaction is provided to a cache of a second master. The transaction is completed. After completing the transaction, a snoop lookup operation corresponding to the snoop request in the cache of the second master is performed. The transaction may be completed prior to or after providing the snoop request. In response to performing the snoop lookup operation, a snoop response may be provided, where the snoop response is provided after completing the transaction. When the snoop response indicates an error, a snoop error may be provided to the first master.