Jenna Fischer: I'm Having a Boy
07/19/2011 AT 08:45 PM EDT
"This is the second grandchild," The Office star corrected, "but first grandson."
When Leno jumped on the word grandson, Fischer confirmed that she and husband Lee Kirk are expecting a boy.
"This is the exclusive, Jay," says Fischer, 37, who appears in the upcoming film A Little Help. "When I went to my movie premiere the other day a reporter asked me if I knew what I was having, and I said I do, but I’m not sharing that yet because I’m [going to] have Jay be the first to know.”
The Office star, who announced her pregnancy in May, had another scoop: the baby is due in the fall.
"September we’re in what they call the home stretch," she says.