A method is for programming a memory block of a non-volatile memory device. The non-volatile memory device is operatively connected to a memory controller, and the memory block defined by a plurality of word lines located between a string select line and a common source line corresponding to the string select line. The method includes programming a first sub-block of the memory block, determining in the non-volatile memory device when a reference word line is programmed during programming of the first sub-block, and partial erasing a second sub-block of the memory block upon determining that the reference word line is programmed during programming of the first sub-block.