The present disclosure provides systems and methods for detecting leakage currents in radio-frequency (RF) ablation systems. An RF generator may be configured to disable an electrical return path from a patient to a ground terminal. The RF generator may also be configured to apply an electrical signal to an electrode that is positioned to be in proximity to target tissue of the patient. The RF generator may be further configured to measure a leakage impedance while the electrical return path is disabled and the electrical signal is applied to the electrode. The RF generator may also be configured to control RF ablation therapy based, at least in part, on the measured leakage impedance. Other features are also claimed and described.