A data processing apparatus has processing circuitry which has a secure domain and a less secure domain of operation. When operating in the secure domain the processing circuitry has access to data that is not accessible in the less secure domain. In response to a control flow altering instruction, processing switches to a program instruction at a target address. Domain selection is performed to determine a selected domain in which the processing circuitry is to operate for the instruction at the target address. Domain checking can be performed to check which domains are allowed to be the selected domain determining the domain selection. A domain check error is triggered if the selected domain in the domain selection is not an allowed selected domain.