Chicago exchange operator CME Group has increased the value of its agreement to buy broker-dealer GFI Group, which is facing a rival bid from brokerage firm BGC Partners.

GFI stockholders would receive $5.25 a share in a mixture of cash and stock. A deal announced in July called for GFI shareholders to receive $4.55 a share in CME stock. The maximum available cash consideration is about 13% of the total consideration, but could be increased to limit proration.