Wireless circuitry may include a radio-frequency amplifier configured to receive a power supply voltage, a load modulation circuit configured to generate a load control signal, and supply voltage error compensation circuitry configured to generate an error signal that is applied to the load control signal to produce a compensated load control signal. The compensated load control signal can be used to tune an adjustable load component of the radio-frequency amplifier. The power supply voltage may exhibit a piecewise constant waveform. The supply voltage error compensation circuitry can include a reference signal generator configured to generate a reference signal and a filter configured to generate a target signal based on the reference signal. The error signal can be computed based on a difference between the target signal and a sensed or estimated version of the power supply voltage received at the amplifier.