Invesco is going to buy OppenheimerFunds, a subsidiary of Massachusetts Mutual Life Insurance, in a more than $5 billion deal, according to a report Friday by Financial Times service Ignites.

The asset manager has been a holding of MassMutual for nearly two decades, but OppenheimerFunds has become steadily less valuable due to pressure from passive trading strategies, such as index funds.

Shares of Invesco fell 1.1 percent in trading.

OppenheimerFunds managed about $250 billion in assets as of the end of last month, according to its website. The asset manager has holdings across a broad range, stretching from global stocks to municipal bonds and more.

MassMutual acquired OppenheimerFunds in 1990 for about $150 million.