It was recently reported that an excess wing exists in the higher frequency side of the dielectric loss peak of some glass-forming materials (including pentachloronitrobenzene). A very careful study of the molecular mobility in pentachloronitrobenzene was carried out using the dielectric technique of thermally stimulated depolarization currents (TSDC). The objectives of this study were (1) to look for an eventual TSDC signature of this excess wing; and (2) to contribute to the elucidation of the nature and origin of this relaxation process. The obtained results show that there is a TSDC signature of the excess wing and suggest that it corresponds to the low temperature flank of the beta-peak, hidden under the largely dominant alpha-peak.