Massachusetts Tax refund amount reduced when I fill the federal form 8606 (after entering backdoor Roth Ira, $6000).

Massachusetts Tax refund amount reduced when I fill the federal form 8606 (after entering backdoor Roth Ira, $6000).  As expected, filling the form 8606 does not change my federal tax due. However, My MA state tax refund goes down, and it should NOT change since my contribution to backdoor Roth IRA is with the after-tax money. How do I fix this?