If H(ejw) is an ideal LPF, what is H(-ejw) ?

Hello all.
Just this simple question:
Let's say that H(ejw) is the frequency response of an ideal LPF, then my question is what is H(-ejw) ??
My guess, is that since I'm not changing w by -w, this is not a simply frequency-reversal operation.
So, may I get any help from the experts?
Thanks

Negating z is a pi-rotation, so you get a high-pass filter.

Thanks.
Yeah. I just figured out my self by doing the math. Thank you anyway for the confirmation.