H1B visa employee and retirement benefits

After 2 years, our employees are 100% vested in the company's qualified retirement plan/ profit-sharing plan which contributes up to 25% of the employee's salary in an investment account. We have an H1B visa holder on a contract for a specific project which was to last about 18 months. The project has taken longer than expected, and now he's been working for us for almost been 2 years. Is he eligible for our profit-sharing plan? Arre we obligated by law to include him in the plan.