One top Wall Street firm is getting less bullish on Micron after the stock’s stunning performance so far this year.

Morgan Stanley lowered its rating to equal-weight from overweight for the chipmaker, citing the company’s fully priced valuation.

“After being bullish on memory for the last two years, we are moving to a neutral stance. DRAM remains strong but looks priced in as MU is very close to our PT,” analyst Joseph Moore said in a note to clients Thursday. “We would rather err on the side of caution in an environment where we can see storm clouds on the horizon.”

The company’s stock is down 2.3 percent in Thursday’s premarket session after the report.

Micron shares are the best-performing chip name in the S&P 500 with a 52 percent gain year-to-date through Wednesday versus the market’s 2 percent gain.

Moore reiterated his $65 price target for Micron shares, representing 4 percent upside to Wednesday’s close.

The analyst is less confident over the strength of the memory market after talking to his corporate sources.

“While data points haven’t meaningfully changed, there is less conviction about a seasonal rebound from our industry contacts than we heard just a few weeks ago,” he said. “Our conversations with cloud buyers indicate more of a mixed picture than we have heard in recent quarters, with everyone getting what they need and some mild pushouts in timing.”

Micron did not immediately respond to a request for comment.

— CNBC’s Michael Bloom contributed to this story.