How to fix a digital clock where the numbers is not fully shown or missing?

Hi. I own an old quartz (raymax) digital clock which is battery operated and not light illuminated. The digits are black/grayish just like in a calculator. There is just one part missing and it can not differentiate between 5 and 6. so if it is 6 in the clock it would be shown as 5.... anyway i can fix this?? Thanks