A 47-year-old Vacaville man learned Sunday that a jar of Skippy peanut butter is no match for an airport security X-ray machine.

The passenger was hoping to leave Oakland International Airport on a Delta Airlines flight to Los Angeles, but he missed his flight after Transportation Security Administration officers found marijuana concealed in a peanut butter jar in his carry-on bag, officials said.

“Drugs aren’t something we’re looking for,” said TSA spokesman Nico Melendez. “The concern here is that peanut butter is prohibited anyway because of the liquid ban. And when we see something in the X-ray hidden in a jar, we need to find out what it is.”

In this case, it was a small amount of pot, though Melendez did not know the exact weight.

Witnesses said the passenger told authorities he had hidden the marijuana because he didn’t have a medical marijuana card, Melendez said. The passenger was cited for marijuana possession and let go. His name was not released.

The passenger’s vessel of choice was not new, Melendez said. Another passenger tried to smuggle marijuana through security at a Los Angeles airport in November 2011 by using a peanut butter jar, he said.