Intel i5-3570 turbo goes above 3.8 Ghz?

As the thread name says my i5-3570 turbos above its range.

I monitor my CPU usage, temperature and clock speeds at all time, and I have spotted the turbo reaches above 4.0 Ghz.

Is that normal? I think it seems kinda weird.
Is it because the CPU is overvolting?
Is it something I should fear?

It's not a problem at this very moment, but I would just like to know if its something I should pay attention to or just let it pass by.

Thanks in advance, guys! :)