SpaceX is allocating a smaller-than-expected portion of its blockbuster initial public offering to retail investors, according to a person familiar with the matter.

The Elon Musk-led company plans to direct a percentage in the low 20s of the offering to retail buyers, including international individual investors, online brokerages and private-bank clients, the person said.

The allocation is below earlier expectations that roughly 30% of the deal would be reserved for retail investors.

The allocation decisions are almost finalized and could still change, the person said.

SpaceX is set to begin trading Friday, in what is poised to become one of the largest public offerings in history. The company is expected to be valued at about $1.8 trillion.

The reduced allocation suggests institutional demand for the shares has been strong as investors compete for access to the hottest IPO in recent years. Even with a smaller allocation, the retail tranche would still rank among the largest ever for a U.S. IPO of this size.