  The continuum-fitting method is the analysis of the thermal spectrum of the
geometrically thin and optically thick accretion disk around stellar-mass black
holes. A parametrization aiming to test the Kerr nature of astrophysical black
holes was proposed in Ghasemi-Nodehi and Bambi in EPJC 76: 290, 2016. The
metric contains 11 parameters in addition to the mass and spin parameters. One
can recover the Kerr case by setting all parameters to one. In this paper, I
study the continuum-fitting method in Ghasemi-Nodehi-Bambi background. I show
the impact of each of the parameters on the spectra. I then employ \c{hi}2
studies and show that using the continuum-fitting method all parameters of
Ghasemi-Nodehi- Bambi spacetime are degenerate. However, the parameter b9 can
be constrained in the case of a high spin value and the Ghasemi-Nodehi-Bambi
black hole as reference. This degeneracy means that the spectra of the Kerr
case cannot be distinguished from spectra produced in Ghasemi-Nodehi-Bmabi
spacetime. This is a problem as regards measuring the spin of astrophysical
black holes and constrain possible deviations from the Kerr case of General
Relativity.
