"We continued our observations of GRB 100305A with the Gemini-N telescope mounted with the GMOS camera. A sequence of z'-band images has been taken for a total exposure time of 15 min. No clear object is visible in the position of the optical afterglow previously reported (GCN 10473) at the following 3-sigma upper limit: z' > 23.42 mag We also report a corrected error measure in our photometry. The correct magnitude estimates at T0 + 2h are: r' = 23.95 +- 0.30 mag i' = 23.71 +- 0.06 mag We apologize for any inconvenience this may have caused."