Standard & Poor's (S&P) has upgraded the Hunter Hall Australian Value Trust from two stars to three stars following a number of changes to the investment portfolio.

"The changes have addressed issues that we had previously identified as areas of concern," the S&P report said.

The changes were implemented after the investment manager undertook a review of its investment process two years ago, Hunter Hall head of strategy and development Michael Walsh said.

"Since the review we have implemented a number of changes to the Australian Value Trust. These changes included a peer review process and better risk constraints on the portfolio," Walsh said.

According to S&P, the changes also included a more structured approach to portfolio construction, and an improved self discipline.

"We take a positive view of the increased overall portfolio management rigour and other steps that Hunter Hall has taken to improve risk controls, which we previously considered insufficient given the inherent risks of the Australian Value Trust's small and illiquid exposures," S&P fund analyst Tom Mills said.

"Although the Australian Value Trust still invests in small and illiquid stocks, more appropriate rules and constraints are now in place to ensure these exposures are understood and subject to limits."

Walsh said the trust's performance has improved since the changes were implemented.

The trust has delivered a 28.7 per cent return for one year compared to the all ordinaries benchmark return of 21.4 per cent.

Over three years the fund had delivered -5.4 per cent compared with -7.2 per cent of the benchmark.