A new fund could be lighting up in investor portfolios soon.

In what would be a first for the exchange-traded fund industry, a marijuana-based ETF could soon begin trading. The ETF Managers Trust on Thursday filed paperwork with regulators, referring to the fund as Emerging AgroSphere ETF.

The fund wouldn’t track marijuana as a commodity, but instead invest in medical marijuana companies involved in the production or sale of products derived from hemp. It would also buy companies which are in the supply chain of either of those categories. 

There are some caveats:

“The Fund will not invest in any companies that are focused on serving the non-medical marijuana market in the United States, Canada or any other country unless and until such time as the production and sale of non-medical marijuana becomes legal in the United States, Canada or such other country, respectively,” the firm wrote in its filing with the Securities and Exchange Commission.

While the fund has yet to be approved, the push toward legalizing marijuana has been growing. In 2016, roughly 60% of Americans said they favored the legalization of recreational marijuana, as the industry gained support in invalidating the war on drugs and seven states voted to legalize pot for recreational or medical use.

The marijuana industry has seen surging growth of late. Sales grew 30% in 2016, according to Arcview Market Research, and they are seen tripling in four years. In Colorado alone, marijuana revenue topped $1.3 billion, contributing $200 million in taxes to the state’s coffers.

In the filing, the ETF Managers Trust said the fund shares had been approved for listing on the NYSE Arca.