A transition detection circuit (20) and method of operation of such a circuit are provided, the transition detection circuit (20) having pulse generation circuitry (25) to receive an input signal (10) and to generate a pulse signal in response to a transition in the input signal, and pulse detection circuitry (30) to assert an error signal on detection of the pulse signal generated by the pulse generation circuitry. The pulse generation circuitry has pulse control circuitry (35) to control a property of the pulse signal dependent on a timing window indication signal (40). In particular, when the pulse signal is generated at least partly whilst the timing window indication signal is set, the pulse control circuitry (35) controls the property of the pulse signal such that generated pulse signal is detected by the pulse detection circuitry (20). In contrast, when the pulse signal is entirely generated whilst the timing window indication signal (40) is cleared, the pulse control circuitry (35) controls the property of the pulse signal such that the generated pulse signal is undetected by the pulse detection circuitry (20). This gives rise to significant area and energy consumption savings, whilst still allowing reliable detection of timing errors.