Jesse Tyler Ferguson, who co-stars on ABC's Modern Family, will join Illinois Lt. Governor Sheila Simon in Chicago on Wednesday to lobby lawmakers to legalize gay marriage.

Illinois lawmakers, who legalized civil unions for gay couples 2 years ago, are expected to take up the issue when they reconvene for a lame-duck session in January.

“It is our responsibility to ensure that everyone is treated equally under the law, and right now we have a group of citizens that we are treating as second-class,” said Simon in a statement. “Bringing marriage equality to Illinois is the right thing to do, and I appreciate the hard work by Rep. Greg Harris, Sen. Heather Steans and three-time Emmy nominee Jesse Tyler Ferguson to bring much-deserved attention to this issue.”

Ferguson and his lawyer fiance, Justin Mikita, in September launched the non-profit Tie The Knot, which sells limited edition bow ties with profits benefiting organizations seeking to expand marriage rights for gay couples. Simon, Ferguson and Mikita on Wednesday will visit The Tie Bar in Naperville to unveil a limited-edition Signature Black Wedding bow tie. On Thursday, they will join other gay marriage advocates in Springfield for a Bow Tie Lobby Day.

“Justin and I are thrilled to be participating in Springfield's Bow Tie Lobby Day,” Ferguson said. “Drawing attention to the importance of marriage equality at this level is exactly why we developed Tie The Knot. We are also excited to see how the citizens and legislators of Illinois do with their bow tying skills.”

(Related: Obama calls on Illinois lawmakers to approve gay marriage.)