Upper panel: pulse frequency of GX 301–2 observed with GBM Pulsar Project. Lower panel: X-ray count rate seen by Swift/BAT in energy range 15–50 keV. Dashed blue lines show the dates when the NuSTAR observations were performed. In each panel the recent spin-up episode is zoomed-in, with the periastron passages marked with the dashed red lines and the apastron passages shown with the dotted blue lines.