A sensor is configured to sense a deflection angle and to transmit a second signal representing the sensed deflection angle to a downhole control unit. The downhole control unit is configured receive signals from at least the sensor. An adjustable bent sub assembly is mechanically coupled to the power section. The adjustable bent sub assembly is configured to, while the downhole motor is in the wellbore, adjust the deflection angle to the desired deflection angle. A biasing mechanism is communicatively coupled to the downhole control unit and mechanically coupled to the adjustable bent sub assembly. The biasing mechanism is configured to, while the downhole motor is in the wellbore, actuate the adjustable bent sub assembly responsive to the downhole control unit. A locking mechanism is coupled to the adjustable bent sub assembly. The locking mechanism is configured to lock the desired deflection angle.