The board of the state pension fund voted Tuesday 5-to-4 to approve a new compensation plan that would raise potential bonuses for investment staff.

State treasurer Steve Grossman, who is chairman of the $50 billion pension board, voted against the plan because it lacked a key provision he supported. Grossman had pushed for bonuses to be linked to the fund’s 8 percent annual return goal; in years when the fund doesn’t hit that threshold, the ultimate bill to taxpayers increases.