Sofia Vergara loses ''control'' of her mouth when she's tired.

The 'Hot Pursuit' actress' co-star Reese Witherspoon has revealed the bilingual star is hilarious to work with on set because her English fades and she ends up saying things which don't make sense.

Reese, 39, said: ''She made me laugh all the time, she was so funny.

''When she gets tired she does this pronunciation thing which is so funny. It's like, 'What is she saying?!' ''

The Colombian-born beauty - who is set to marry 'Magic Mike XXL' actor Joe Manganiello on November 22 after they got engaged last year - explained she struggles to differentiate between Spanish and English when she's been on set for a long time which is what leads to her bizarre mumblings.

She joked: ''I lose my perfect English, I lost it when I'm tired. It gets really weird. My mouth keeps talking but I've already lost control of it.''

And although her exhausted conversations can be hysterically funny, she confessed it ''ruined'' scenes when they were trying to shoot the comedy movie.

She added: ''Yeah I ruined a lot of takes!''

Despite Sofia's strange habit, the pair admitted they are eager to work together on future movies.

Asked if they would act opposite each other again, Sofia told British chat show 'Lorraine': ''Well, if Reese keeps producing things [then yes].''

To which Reese said: ''Well if she still shows up and she's still as funny as she is in this movie...''