Johnny Galecki learned this weekend that his pregnant girlfriend Alaina Meyer is expecting a boy.

"A day I'll never forget," "The Big Bang Theory" alum, 43, captioned a photo of Meyer, 21, standing over him and kissing his lips as he kneels.

They are both covered in blue paint. reported Galecki, Meyer and their loved ones ate cupcakes and other treats as they celebrated at the outdoor gender reveal party on Sunday.

The couple announced earlier this month that they are expecting their first child, but they did not say if it would be a boy or a girl.

Photo credit: Johnny Galecki / Instagram