"On March 5.42 UT we observed the field of GRB 100305A (Troja et al., GCN 10470) with the Gemini-N telescope and the GMOS instrument. In our 300s r'-band and 900s i'-band images we clearly detect a source inside the XRT error circle at the following position: RA (J2000) = 11:13:28.30 Dec (J2000) = 42:24:10.50 with an uncertainty of 0.5" in each coordinate. Using 2 USNO-B1 stars we calibrated our photometry and obtained r' = 23.95 +- 0.30 mag i' = 23.71 +- 0.50 mag At the moment no evidence of fading can be addressed. Further analysis are in progress. We thank the Gemini staff for performing this observation, in particular Andrew Stephens."