Mattel Inc. (NASDAQ:MAT) shares jumped about 25% on Thursday afternoon. That puts the toy maker on track for its biggest one-day gain since 1996.

The stock traded near $15.80, up from Wednesday’s close of $12.66.

Authentic Brands Group has been privately discussing a takeover offer that could top $20 per share and value the Barbie maker at around $6 billion or more. That would be about 58% above Wednesday’s closing price.

Before the Wall Street Journal reported on the deal, Mattel was worth about $3.6 billion.

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