35 ILCS 636/5-55

If a municipality has, by contract, pledged or dedicated any or all of the revenues collected under any of its taxes imposed pursuant to subparagraph 1 of Section 8-11-2 of the Illinois Municipal Code, Section 8-11-17 of the Illinois Municipal Code, or Section 20 of the Telecommunications Infrastructure Maintenance Fee Act as shown on the list described in Section 5-25 of this Act, then the equivalent portion of revenues collected from the tax authorized by this Act shall be deemed pledged or dedicated in a manner substantially similar to the pledge of the then existing taxes so as to prevent disruption of such contract.