Dennis Gartman gets short

An uptick in market volatility this week and a breach of key trend lines has led Dennis Gartman to change his position on stocks.

For months, the author of "The Gartman Letter" has repeated the same sentiment regarding his market view. "It's still a bull market; why fight it?" Gartman said in a CNBC interview on Dec. 24.

On Jan. 5, Gartman was asked whether he'd buy U.S. equities on a day when the Dow dropped 319 points. "Give me another 200 points down on the Dow, you bet I will," he said.

But on Wednesday, Gartman said that he was now net short of stocks. "As of this afternoon, I am slightly, very slightly net short," he said on CNBC's "Fast Money."

According to Gartman, the price action over the past week is a bearish indicator for stocks going forward. "It was amazing how things have changed so dramatically in the course of a week," he said. "Trend lines are now being broken."

Gartman also commented that Tuesday's reversal to the downside was "just devastating."

Despite his overall net short position, Gartman said he was maintaining a couple of key long positions, namely in aluminum stocks and oil tankers.