Methods and arrangements in a codec for supporting bandwidth extension, BWE, of an harmonic audio signal. The method in the decoder part of the codec comprises receiving a plurality of gain values associated with a frequency band b and a number of adjacent frequency bands of band b. The method further comprises determining whether a reconstructed corresponding frequency band b′ comprises a spectral peak. When the band b′ comprises a spectral peak, a gain value associated with the band b′ is set to a first value based on the received plurality of gain values; and otherwise the gain value is set to a second value based on the received plurality of gain values. The suggested technology enables bringing gain values into agreement with peak positions in a bandwidth extended frequency region.