Typing /ga and pressing [TAB] results in /game

When typing /ga or /gam and hitting TAB results in /game, which is not a real command, instead of /gamemode, which is the fist "g" command in alphabetical order. However, typing /g and hitting TAB results in the correct command /gamemode.

This may just be on my computer, but it seems very weird. I do not know how this would happen on just my computer.