Actor not given credit on IMDB cast listing

I am requesting a manual data correction for the Death Valley Days episode " Fifteen Paces to Fame". The automated submission system keeps rejecting the fix.
Death Valley Days
S6.E6
Fifteen Paces to Fame
Episode aired Nov 7, 1957
As a editorialist in Virginia City, a young Mark Twain finds himself facing a gun duel with a rival newspaper man.

This episode is about Samuel Clemens/Mark Twain. This is also clearly referenced in the trivia section. Note in the cast listing there is no listing for either Samuel Clemens or Mark Twain, but there are two listings for the character Ganse Taylor who is played by Doug McClure in the episode. Clearly Paul Donovan plays the character Mark Twain. It's quite obvious he is not playing two parts and is not playing the part of Ganse Taylor.