Brookfield Asset Management Ltd.’s A$19.4 billion ($12.4 billion) contested takeover offer for Origin Energy Ltd. won more advisory firm support ahead of a key vote on the deal.

The A$9.53 per share proposal by Brookfield and partners including EIG Global Energy Partners “offers investors certainty of value at a level that is within a reasonable range,” CGI Glass Lewis said in a note to clients.

Origin’s largest shareholder AustralianSuper opposes the deal, arguing the price is well below the Sydney-based utility’s long-term value. Australia’s biggest pension fund last week raised its holding to about 15%.

A block of 22.8 million shares in Origin, equivalent to 1.3% of the company’s float, traded Thursday at a market value of about A$199 million. AustralianSuper declined to comment on whether it had purchased the stake.

Though there’s some merit to AustralianSuper’s view that an independent expert’s valuation of Origin is too low, the fund’s opposition relies on a “fundamentally more positive outlook with respect to long-term value,” CGI Glass Lewis said in its report, recommending investors vote in favor of the deal at a Nov. 23 meeting.

The proxy firm follows Institutional Shareholder Services, which this week also recommended investors back the Brookfield-led offer.

Origin shares rose as much as 1.6% to A$8.88 in Sydney trading Thursday as of 1:20 p.m. local time.

Australian rules require a minimum of 75% of participating shareholders to approve a takeover offer, meaning 15% opposition has usually proved sufficient to block a deal as typically not all retail investors will cast a ballot.

Brookfield is seeking to add Origin to gain more exposure to Australia’s energy transition, and intends to spend as much as A$30 billion over 10 years to accelerate the utility’s shift from fossil fuels to cleaner energy.

--With assistance from Amy Bainbridge.

(Updates with AustralianSuper declined to comment, share prices)