To Serve and To Praise 6

In Maseches Sotah 34b, Rava records that Calev prostrated himself on the graves of the Avos and "he said to them: 'My forefathers, pray for me that I be saved from the plan of the spies!'"  The Gemara seems to approve of Calev's action.  Was Calev in violation of Rambam's fifth fundamental principle of Judaism?