It's safe to say that Chicago's Erik Schroeder will always remember his 30th birthday.



He's known for some time that he wanted to propose to his girlfriend, Nina O'Keefe, but the holidays and Valentine's Day passed without him popping the question.



"I asked myself what I wanted for my 30th birthday, and then I realized that all I wanted was for her to marry me," Schroeder said.



The only question left was how he would propose.



O'Keefe is an actress currently starring in "Heddatron," a Sideshow Theatre Company play that's currently running at Steppenwolf Garage Theatre, so that became the basis of the elaborate ruse.



After Sunday's show, Schroeder was called up on stage, ostensibly so the cast, crowd and the robots involved in the play could sing happy birthday, but instead of receiving the birthday song -- and prompted by a robot -- Schroeder pulled out a ring and proposed to his girlfriend of six years (watch video below).



"It was my great grandmother's sister's ring," said Schroeder. "She had to take off the costume ring she was wearing for the play, but I was lucky because it fit perfectly."



And of course, O'Keefe said yes.



"Like I said in the video, she's my best friend, so the thought that she wouldn't say yes didn't even cross my mind," said Schroeder, who works for Lookingglass Theatre Company.



A date has not been set for the nuptials.