cwtfilterbank magnitude linear scale

I am using the cwtfilterbank function to generate a scalogram from a signal. However, the frequencies on the Y-axis of the scalogram are not linear. I have read the documentation for cwtfilterbank, but I couldn't find a direct solution. What changes can I make to achieve a linear frequency scale on the scalogram?

fb = cwtfilterbank('SignalLength',signalLength,'Wavelet','amor','SamplingFrequency',Fs,'VoicesPerOctave',48, 'FrequencyLimits', [0 40])
[wt,f] = fb.wt(sig);
im = ind2rgb(im2uint8(rescale(abs(wt))),jet(256));