Bill Gross’s Pimco Total Return Fund, the world’s largest mutual fund, suffered the first client withdrawals since 2011 last month as global bond markets tumbled the most in nine years.

Investors pulled $1.32 billion from the $285 billion fund, according to estimates from Chicago-based research firm Morningstar Inc. An exchange-traded version of the Total Return fund saw clients pull an estimated $64.4 million, the first ever withdrawals since the ETF’s inception in 2012.

A bet on U.S. government debt hurt Gross last month as Treasurys tumbled 2 percent amid speculation a strengthening U.S. economy will allow the Federal Reserve to reduce its monetary stimulus. Gross’s fund declined 1.9 percent last month through May 30, its biggest monthly loss since September 2008, to trail 94 percent of peers, according to data compiled by Bloomberg. Gross raised the holdings of Treasurys in his fund to 39 percent as of April 30, the highest level since July 2010, and has increased the proportion of U.S. government securities every month this year since February.

Global bond markets posted their biggest monthly losses in nine years in May as the U.S. dollar rallied and stocks reached record highs. The more than $40 trillion of bonds in the Bank of America Merrill Lynch Global Broad Market Index fell 1.5 percent on average.

2011 ‘Stinker’

The last time investors pulled money from Gross’s fund was in December 2011. The fund had its first ever annual redemptions that year of about $5 billion after Gross eliminated U.S. Treasurys early in the year and missed a rally in what he called a “stinker” of a performance. The Total Return fund rose 4.2 percent in 2011, behind 70 percent of peers, according to data compiled by Bloomberg. Over the past five years, Gross’s fund has advanced 7.5 percent, ahead of 93 percent of rivals.

Mark Porterfield, a spokesman for Newport Beach, California-based Pacific Investment Management Co., said the firm doesn’t comment on client deposits or redemptions.

Morningstar estimates deposits or withdrawals for mutual funds by computing the change in assets on a monthly basis that isn’t accounted for by performance. The fund’s actual withdrawals or deposits may differ from Morningstar’s estimates because of the timing of purchases and redemptions or dividend distributions.