Speedo is 10mph off, how can i fix this?

My speedo is 10mph off, but it doesn't need a new gear. I know this because it's ALWAYS 10mph off. I've got a T5, 3.55s, and a 23 tooth gear. When i'm going 25 it reads 35 and when i'm going 75 it reads 85. So, i just basically need to move the needle "back" 10mph. Is there any way to do this other than taking apart the instrument cluster, removing the speedo needle, and putting the needle back on while i'm driving? I guess i could do this on a set of jack stands, but isn't there a better way?

Thanks for the link, jrichker. Looks like that fix will work, but i'll have to remove the 23 tooth and go BACK to a 17 tooth and then change the drive gears as well.

I think i'll just live with the error rather than go through all that trouble.