keybinds

So, my Minecraft restarted on it's own 2 days ago and when I opened it back up all of my settings, key binds, textures, skins were all reset. So I went to fix everything and it all worked. but when I went to fix my key binds they wouldn't work. The buttons that it wouldn't let me bind were, mouse button 4, and mouse button 5.Idk if I'm the only one with the issue but if there is a solution please let me know