Sarah Michelle Gellar and Freddie Prinze Jr., who have been together for so long that we're surprised they didn't have kids before this, are now expecting their first child together, a source close to the couple confirms.

"They're very excited," says the source, adding that the actress, 31, is due in the fall.

Gellar, who has been married to Prinze, 33, for six years, is planning to shoot the HBO pilot The Wonderful Maladays, for which she serves as an executive producer.

Prinze recently shot the comedy pilot No Heroics for ABC.

Freddie Prinze Jr. and Sarah Michelle Gellar got married in an intimate ceremony back on September 1, 2002, in Mexico. They first met in 1996 on the set of I Know What You Did Last Summer but didn't begin dating until January 2000.

Congrats to the happy couple!