Invert / Equalize a minimum phase filter (phase delay)

This is no doubt a very stupid question, but if I have a minimum phase 1st order IIR filter, e.g.

b = [0.68655712709822769, 0.41193427625893658];

a = [1, 0.098491403357164345];

and I wish to build the inverse / equalizer for it, I expect it to be

be = a;

ae = b;

but when I look at the equalizer with fvtool:

fvtool(be, ae, 'freq')

I see that the phase response is +ve everywhere, and so the phase delay shown in fvtool is -ve everywhere (which to me means non-causal).

I'm pretty sure the inverse of a minimum phase filter should be causal and stable, so can anyone tell me how to change be and ae (or something in fvtool) to get a plot of a "sensible" phase delay?

Thanks, Andrew