Illinois’ taxation of retirement income

When my 401k expired and I had to begin receiving mandatory payouts from my personal IRA (which was funded by the 401k funds) I begin receiving significant quarterly payouts that were fully taxable on my federal return, and were reported on line 4b. However, the Illinois return states that taxable amounts on line 4b of the federal return are not taxable on my state return. This is a substantial portion of my annual income and it’s hard to believe it is tax free in Illinois. Illinois Pub. 120 seems to reinforce the idea that it is tax free, but it seems to good to be true. Am I dreaming?