A method includes accepting an input code word, which was produced by encoding data with an Error Correction Code (ECC), for decoding by a hardware-implemented ECC decoder. The input code word is pre-processed to produce a pre-processed code word, such that a first number of bit transitions that occur in the hardware-implemented ECC decoder while decoding the pre-processed code word is smaller than a second number of the bit transitions that would occur in the ECC decoder in decoding the input code word. The pre-processed code word is decoded using the ECC decoder, and the data is recovered from the decoded pre-processed code word.