Japan’s Government Pension Investment Fund is emerging as an important source of demand for the nation’s debt just as the central bank plans to reduce bond purchases.

The GPIF’s holdings of government bonds increased 25% to ¥50.3 trillion ($311 billion) in the fiscal year ended March 31, according to Bloomberg analysis of data from the fund released last week. This happened just as the proportion of the nation’s treasury bills, non-government debt and a currency-hedged foreign debt in its portfolio all fell.

While the GPIF’s holdings of government bonds are less than a 10th of the Bank of Japan’s, the fund’s tendency to buy on dips helps limit losses in the fixed-income market, especially when it’s weighed down by concern over a rapid decrease in the BOJ’s debt buying.