Washington — Congress approved a series of changes in recent months aimed at helping low-income college graduates repay their government-backed loans. For some of those graduates, however, the changes may not have gone far enough, advocates say.

One problem involves a provision establishing a new income-based repayment plan, which would help college graduates who have spent years trying to pay back their loans but still aren’t making enough money to catch up. Supporters of the provision warn that the language, as written by Congress, will require some married couples, in which each partner is eligible for income-based repayment of a student loan, to pay twice as much as two unmarried borrowers in a similar financial situation would pay. This “double-counting penalty” arises for couples who file joint income-tax returns, because the couple’s entire income would be used to calculate how much each spouse pays individually.

Another problem involves a provision that will forgive the federally guaranteed loans of college graduates who work at least 10 years in certain public-service professions. That language, according to some supporters, didn’t establish procedures for letting graduates know ahead of time which specific jobs would qualify for the loan forgiveness.

More than 1,500 people and more than a dozen national organizations submitted comments asking the Education Department to deal with those two issues when it was writing regulatory language for carrying out the programs. But the department, in final regulations it issued late last week, did not do so, according to the Project on Student Debt, an advocacy group based in California.

The Education Department still might be able to find ways outside of the regulatory process for helping borrowers in the public-service loan-forgiveness program figure out which jobs are eligible, said Robert M. Shireman, executive director of the Project on Student Debt.

The double-counting penalty in the income-based repayment plan, however, might need the renewed attention of lawmakers, Mr. Shireman said. “This is obviously unfair and inappropriate,” he said of the problem facing some married couples, “and needs to be changed by Congress.”

An Education Department spokeswoman, Samara Yudof, said she agreed the double-counting issue was a matter of statutory language in the legislation that would require Congressional action to change.

The regulations for the public-service loan-forgiveness program “are clear and provide a broad list of eligible occupations,” Ms. Yudof said. Department officials can identify those eligible occupations in the paperwork they give applicants, but the officials avoid using regulations to prescribe specific forms so that their successors can make improvements in future years, she said. —Paul Basken