On the same day that Moody’s announced its credit rating downgrade of Berkshire Hathaway, Doug Kass — who’s made some hay by being short on Berkshire shares for the past year — writes on TheStreet.com that he’s now bullish on Warren Buffett’s firm.

“When conditions change, as they appear to be doing now … opinions must change, and opportunities must be embraced,” writes Kass. “This is especially true in the case of Berkshire Hathaway as the considerations that led to my shorting of Berkshire Hathaway’s shares at around $145,000 a share have now reversed, and, with the shares today trading under $90,000 a share, I have begun to accumulate a long position in Berkshire Hathaway.”

Kass says he estimates the value of Berkshire’s investment portfolio at about $73,000 a share, “so I am paying less than 3.5 times after-tax operating earnings for the non-investment assets” of the company.

Kass also says that, using the view of intrinsic value that Buffett himself has described, Berkshire’s intrinsic value is now about 30% higher than its share price. Kass, who called a market bottom back in early March, says he expects markets to continue to rise, with financials like Wells Fargo — a major Berkshire holding — leading the way, which will add to the value of Berkshire’s investment portfolio. The company’s intrinsic value “will likely be much higher by midyear”, Kass says, adding that he doesn’t think the Moody’s downgrade will have much of a negative impact on Berkshire’s balance sheet and income statement.

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