Analysis of a large set of phase-resolved K -band spectra of the cataclysmic variable WZ Sge shows that the secondary star of this system appears to be an L-dwarf .
Previous K -band spectra of WZ Sge found that the CO overtone bandheads were in emission .
We show that absorption from the ^ { 12 } CO _ { ( 2 , 0 ) } bandhead of the donor star creates a dip in the ^ { 12 } CO _ { ( 2 , 0 ) } emission feature .
Measuring the motion of this feature over the orbital period , we construct a radial velocity curve that gives a velocity amplitude of K _ { abs } = 520 \pm 35 km s ^ { -1 } , consistent with the previously published values for this parameter .