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High signal-to-noise ratio spectroscopic observations of the BL Lac object S40954+65 at the alleged redshift z = 0.367 are presented. This source wasdetected at gamma frequencies by MAGIC (TeV) and FERMI (GeV) telescopes duringa remarkable outburst that occurred in February 2015, making the determinationof its distance particularly relevant for our understanding of the propertiesof the Extragalactic Background Light. Contrary to previous reports on theredshift, we found that the optical spectrum is featureless at an equivalentwidth limit of \sim 0.1 Ang. A critical analysis of the existing observationsindicates that the redshift is still unknown. Based on the new data we estimatea lower limit to the redshift at z \geq 0.45.

What is the redshift of the gamma- ray BL Lac source S4 0954+65?