Warren Buffett disagrees with Elon Musk's assessment of one of his main investing tenets.

Buffett has long advised investors to look for companies that have a "moat," or enough of a buffer around them to maintain a competitive advantage over industry peers in terms of brand strength and business model.

Telsa's Musk said this week that "moats are lame" and "what matters is the pace of innovation."

But Buffett says he believe companies with strong and sustainable moats do exist.