Gate-protection circuitry protects a transistor, such as a MOSFET, from large gate-to-source voltage differentials that can permanently damage the transistor's gate-oxide layer. A source-voltage detector selectively enables the gate-protection circuitry based on a source voltage of the transistor. The gate-protection circuit is implemented without any Zener diodes. The transistor may be a load switch that is selectively controlled to apply a supply voltage to a load.