Zero-tail Discrete Fourier Transform-spread OFDM (ZT DFT-s-OFDM) modulation replaces the Cyclic Prefix (CP) with a low power tail whose length can be dynamically configured to cope with the instantaneous delay spread of the channel. In this paper, we discuss the reference sequence design for ZT DFT-s-OFDM. Our proposed approach is based on a deliberate distortion of the known Zadoff-Chu (ZC) sequences aiming at adapting them to the ZT DFT-s-OFDM waveform while preserving their attractive properties. A numerical analysis confirms the validity of our design in generating ZT DFT-s-OFDM reference sequences with zero autocorrelation, limited cross-correlation, flat frequency response and low Peak-to-Average Power Ratio (PAPR).