Kaley Cuoco's The Big Bang Theory castmate Jim Parson accidentally blew her birthday surprise.

The 45-year-old actor was so excited to give his co-star her birthday cake that he shared a photo of the confectionery online Thursday.

While the public post alone could have let the cat out of the bag, the actor behind Sheldon completely exposed the secret treat when he tagged the birthday girl herself, writing: 'Almost time, @kaleycuoco ... shh.'

Whoops! Kaley Cuoco's birthday surprise from the cast and crew of The Big Bang Theory was accidentally spoiled by castmate Jim Parsons (together in 2016) 

Really? The actor behind Sheldon completely exposed the secret treat when he tagged the birthday girl herself, writing: 'Almost time, @kaleycuoco ... shh'

The pink, rainbow sprinkle adorned cake read 'Happy Birthday Kaley' and looked delectable.

Jim's 'at' tag got Kaley's attention, prompting a funny follow-up.

A sour looking Kaley held up her phone to show the 'surprise' cake and Jim captioned the pic simply: 'Oops.

Too sweet to keep a secret? The pink, rainbow sprinkle adorned cake read 'Happy Birthday Kaley' and looked delectable

Kaley's actual birthday is today, Friday November 30.

The Big Bang Theory team just began shooting their 12th and final season together.

Kaley is looking forward to living life without the rigorous shooting schedule of a network sitcom, according to E! News.

Last hurrah! The Big Bang Theory team just began shooting their 12th and final season together

A source close to the actress said the newly married thespian, who wed equestrian Karl Cook over the summer, said she's loving married life.

'Kaley and Karl are super happy still, they love each other and love being married,'  they said.

'He isn't home a lot though, he works remotely four or five days a week so her weekends are mostly devoted to spending time with him.'

Honeymooners! A source close to the actress told E! the newly married thespian, who wed equestrian Karl Cook over the summer, said she's loving married life. The pair are seen above earlier this month