There is provided mechanisms for beamforming using an antenna array. A method is performed by a network node. The method comprises obtaining, from a wireless device, a precoding matrix indicator to be used for transmission to the wireless device. The method comprises selecting a codebook from a set of codebooks according to the received indicator, wherein the selected codebook defines the precoding matrix, and wherein the set of codebooks comprises codebooks defining variable beam widths and having same number of non-zero antenna weights for all beam widths. The method comprises precoding transmission of signals to the wireless device from the antenna array using the selected codebook.