Methods, systems, and devices are described for wireless communications. A transmitting device may generate first encoded bits by encoding first information bits using a polar code of a first size, N, and transmit the first encoded bits to a receiving device. After determining the receiving device failed to decode the encoded bits, the transmitting device may generate second encoded bits by encoding the first information bits using a polar code of a second size, 2N. In some cases, the transmitting device may use the first encoded bits and one or more copied information bits to generate the second encoded bits. The transmitting device may transmit the second encoded bits to the receiving device, along with an indication of the number of copied information bits used to generate the second encoded bits. The number of copied information bits may be based on changing channel conditions or transmission parameters.