It happens to the best of us. Sometimes it's just so hard to keep celebrities from getting into spats at our $3 million birthday parties.

Just ask Leonardo DiCaprio. At his posh New York birthday celebration, there was a bit of a tiff between a couple of names you might recognize: Robert De Niro and Jay-Z.

You don’t get anywhere in celeb circles without learning that you do not cross Bobby D -- something Jay-Z soon learned.

According to a Page Six spy, Hova approached De Niro at Leo’s party to say hello, and the actor got a little gruff with him.

Sources say Jay-Z, a fellow TriBeCa resident, was supposed to record a special song for the film festival of the same name spearheaded by De Niro. But when Bobby tried to contact Jay-Z to discuss the details, his calls went unanswered.

Dude. Who doesn’t return Robert De Niro’s calls?

Jay-Z tried to joke his way out of it by saying he’s bad on the phone, but De Niro would have none of it. The tattletale said, “He told Jay that if somebody calls you six times, you call them back. It doesn’t matter who you are, that is just rude.”

Ever the dutiful wife, the beautiful Beyonce even tried to intervene, but to no avail. If De Niro decides you're disrespectful, then you pretty much are.

The spat was the talk of the party, but a source close to De Niro says it wasn’t as big as it seems: “It was a low-key private conversation between two people that was apparently overheard. It was not a heated discussion.”

The takeaway? Nobody sends De Niro to voicemail. Nobody.