Digital pre-distortion is a powerful technique in combating nonlinear distortion caused by power amplifier. However, due to impairment such as I/Q imbalance in feedback path, the linearization performance can be greatly degraded. Moreover, in wideband PA linearization system, I/Q imbalance in feedback path can be frequency-dependent, which complicates the design of the DPD. In this paper, we present a mitigation method, which compensates I/Q imbalance utilizing proper nature of power amplifier output signal. The proposed method is totally blind and no external calibration signal is needed. Meanwhile, fast convergence is achieved compared to existing properness-based I/Q compensation algorithms. Effectiveness of the proposed technique is verified by computer simulations.