It turns out my book Warren’s Mistakes was wrong.

Warren Buffett’s biggest mistake wasn’t buying BNSF Railway with Berkshire Hathaway stock, like the book claims. It wasn’t selling McDonald’s (MCD) to buy Dairy Queen. It wasn’t even losing billions running NetJets – which is one of the worst capital allocation decisions of all time. And it wasn’t even buying $40 billion worth of windmills because of the false belief that America was running out of oil.

Buffett’s biggest mistake ever was his friendship with Microsoft founder Bill Gates and the resulting decision to give away his entire fortune by 2034. The graveyard of good intentions has a new headstone – Warren Buffett’s.

This morning, Buffett announced he is withholding his annual gift to the Gates Foundation while an outside review picks through the foundation’s ties to Jeffrey Epstein – the scandal now swallowing Bill Gates whole. Just remember: Gates established his relationship with Epstein after Epstein served jail time for soliciting teenagers in Palm Beach. It’s hard to believe that Buffett didn’t know about that until now.