You might want to be careful about what you call Ryan Gosling's girlfriend.

The 32-year-old star of The Notebook reportedly lost his cool when a photographer said the word "baby" to refer to Ryan's girlfriend, Eva Mendes, according to the New York Post.

Ryan and Eva  who have been dating since September 2011  were at the Bowery Hotel in NYC to promote their new film, The Place Beyond the Pines.

A photographer at the event  who had recently taken pictures of Eva at a different event  saw the actress and shouted "Hey, baby!" to her. Ryan did not take kindly to this.

"Ryan completely flipped out, and it got heated," says an onlooker.  

"Ryan got in the guy’s face and said, ‘Who are you calling baby?'" the source continues. "Eva had to jump in and calm everyone down before it came to fisticuffs."

However, it sounds like cooler heads eventually prevailed.

"Ryan then made nice and shook the guy’s hand,” continues the source. 

Meanwhile, once they made their way into the actual event, it sounds like Ryan and Eva did their best to not get all cuddly at the work function.

“I didn’t see Eva and Ryan interact once,” a source says about Ryan and Eva, as Ryan adorably spent time with his mom at the party and left separately from Eva. 

“[Ryan and Eva] stayed at opposite ends of the room from one another,” adds the insider.

We're just glad Ryan didn't do anything "crazy" or "stupid" to that photographer.

Source: New York Post