Shares of National CineMedia Inc. soared Wednesday, after movie theater operator AMC Entertainment Holdings Inc. disclosed that it acquired a large stake in the cinema advertising network operator.

In a 13G filing with the Securities and Exchange Commission late Tuesday, AMC AMC, +10.16% said it owned 5.95 million shares of National CineMedia NCMI, +0.69%, or 6.8% of the shares outstanding. That would make AMC the third largest shareholder, according to data provided by FactSet.

The 13G filing implies a passive investment, which suggests AMC doesn’t intend to make changes at the company.

National CineMedia’s stock shot up 18.6% in premarket trading. It had gained 2.1% the past two days, after closing at a record low of $1.42 on Friday and Thursday.

Based on Tuesday’s closing price of $1.45, the shares AMC now owns would be valued at $8.63 million.

Meanwhile, AMC’s “meme” stock rose 0.8% ahead of the open. It has run up 24.4% over the past four days, since closing at a one-year low of $10.37 on May 11.

Over the past 12 months, National CineMedia’s stock has plunged 68.2% through Tuesday, while AMC shares have slipped 8.1% and the S&P 500 index SPX, +2.02% has eased 0.9%.

The disclosure of AMC’s investment in a cinema advertising company may not be such a surprise for investors, especially when compared with the disclosure two months ago of an investment in Hycroft Mining Holding Corp. HYMC, , which is a gold and silver miner.

Days before the Hycroft investment was announced, the miner’s stock had closed at a record low of 29 cents. It closed Tuesday at $1.34.