Plan mode not showing sum of hours

While planning a Sprint on Rapid Board if added more than 999h on the Sprint it will not show the sum of sprint hours.

Steps to reproduce:

1- Add more than 999 hours to any issue; (it will show properly)

2- Go to Report view then go back to Plan Mode;

The best example of the problem:

Environment:

JIRA 5.0.6 to 5.1.3
GreenHopper 6.0.1 to 6.0.3