Tara Siegel Bernard / New York Times News Service

Now that same-sex marriage has been legalized in New York, at least a few large companies are requiring their employees to tie the knot if they want their partners to qualify for health insurance.

Corning, IBM and Raytheon all provide domestic partner benefits to employees with same-sex partners in states where they cannot marry. But now that they can legally wed in New York, five other states and the District of Columbia, they will be required to do so if they want their partners to be covered for a routine checkup or a root canal.

But some gay and lesbian advocates are arguing that the change may have come too soon: Some couples may face complications, since their unions are not recognized by the federal government.

“Even with the complications, many people will want to get married for the reasons people want to get married,” said Ross Levi, executive director of the Empire State Pride Agenda. “But from our perspective, to hinge something as important as insurance for your family to what is still a complicated legal matter for same-sex couples doesn’t seem to be a fair thing to do.”

He said that there are a variety of reasons — legal, financial and personal — why companies should keep the domestic partnership option at least until gay marriage is recognized at the federal level. Legally speaking, getting married could create immigration issues or it could potentially muddy the process of adopting a child. The employers making the changes said they spoke regularly with their gay and lesbian employee groups and planned to phase in the requirement.

“My impression is that there has been lots of discussion about dropping domestic partner coverage when marriage is first opened up to same-sex couples, but very few employers actually end up taking this step,” said Jennifer Pizer, legal director at the Williams Institute, which studies sexual orientation law and policy issues.