What is the redshift of the gamma- ray BL Lac source S4 0954+65?
  High signal-to-noise ratio spectroscopic observations of the BL Lac object S4
0954+65 at the alleged redshift z = 0.367 are presented. This source was
detected at gamma frequencies by MAGIC (TeV) and FERMI (GeV) telescopes during
a remarkable outburst that occurred in February 2015, making the determination
of its distance particularly relevant for our understanding of the properties
of the Extragalactic Background Light. Contrary to previous reports on the
redshift, we found that the optical spectrum is featureless at an equivalent
width limit of \sim 0.1 Ang. A critical analysis of the existing observations
indicates that the redshift is still unknown. Based on the new data we estimate
a lower limit to the redshift at z \geq 0.45.
