The letter presents a modification on the block-wise operation of convolutional interleavers for the Parallel Concatenated Block (PCB) codes. Interleaving is conducted so that every block of the interleaved data includes one bit of a message block. This leads to determining the minimum weight of PCB codes from messages with weight 1. Due to the insertion of some stuff bits in the permutation process, multiplicities of the minimum weight of the PCB’s constituent code is less than that obtained from the previously proposed interleavers. This improves the performance of code in its error floor region.