  The centroid energy Ecyc of the cyclotron line in the spectrum of the binary
X-ray pulsar Her X-1 had been found to decrease with time on a time scale of a
few tens of years - surprisingly short astrophysically. This was found for the
pulse phase averaged line centroid energy using observational data from various
X-ray satellites over the time frame 1996 to 2012, establishing a reduction of
about 4 keV. Here we report on the result of a new observation by NuSTAR
performed in August 2015. The earlier results are confirmed and strengthened,
with respect to both, the dependence of Ecyc on flux (it is still present after
2006) and the dependence on time: the long-term decay continued with the same
rate, corresponding to a reduction of about 5 keV in 20 years.
