Question regarding security deposits in Chicago

[Justin Sumulong]

Okay, I'm flipping sides and asking a question regarding my security deposit for a rental I am moving out of in Chicago.

A couple months ago, I asked our landlord if we could move out sooner than the lease end date. (long story short: lease ended in May & we have a baby due in mid-May so we wanted to move & settle before).  My landlord said yes as long as we gave them at least 30 days notice.  Sometime before the end of Feb, we told them we were moving out by the end of March.

Today, they tell us we need to be out by noon tomorrow as per the lease AND THEY ARE KEEPING OUR SECURITY DEPOSIT.  This was never mentioned prior to today and I tried to argue back saying this was not negotiated before.  They are saying it is fair since they are losing out on two months rent for us leaving early.

My question is:  Is this legal for them to keep the security deposit if they approved our early move-out (on record via email) without mention of this before?

Thanks for any & all input.

-Justin