An anonymous passenger brightened a Philadelphia cab driver's night with the tip of a lifetime: nearly $1,000 on a $4.31 fare.

Oumar Maiga's bosses revealed the hefty, holiday-season gratuity Wednesday after waiting to make sure the credit card cleared and it wasn't an error.

The West African immigrant received the $989.98 tip Dec. 13.

Maiga's bosses tell Philly.com (http://bit.ly/1AfGvSZ ) the cabbie and passenger chatted briefly during the mile-long trip from the city's Old City section to Columbus Boulevard.

Maiga said his shift had been a little hectic. The passenger said he'd make it a great night and punched in the tip.

Maiga asked if he'd made a mistake. The passenger replied, "I know what I did."

Maiga's bosses said the card company wouldn't give up the mystery tipper's name.