A method of operating a memory system includes reading data of first memory cells, the first memory cells being connected to a first wordline from among a plurality of wordlines, the plurality of wordlines including one or more dummy wordlines and one or more normal wordlines; determining whether the first wordline is one of the one or more dummy wordlines by determining, based on the read data, a number of the first memory cells having a first threshold voltage state, the one or more dummy wordlines being wordlines the memory cells of which have been programmed with dummy data, the one or more normal wordlines being wordlines that are not dummy wordlines; and performing a repair algorithm for correcting an error in the read data, selectively according to a result of the determination.