Indiana senators on Thursday approved a proposed constitutional amendment that would ban gay marriage, Indianapolis CBS affiliate WISH-TV reported.

In a 38 to 10 vote, the state Senate voted in favor of Republican Senator Carlin Yoder's amendment that seeks to ban civil unions for gay couples as well as marriage. The measure now heads to the Indiana House.

“The Marriage Discrimination Amendment violates every Hoosier's basic right to fairness and equality,” Randy Studt, president of the gay rights group Indiana Equality, said in a statement. “It's just an attempt to distract Hoosiers from the greater issues facing Indiana, threatening our state's current and future economic development.”

Both chambers of the Assembly need to approve the resolution twice before voters can weigh in on the issue.

Indiana law already prohibits gay marriage, but opponents worry gay activists could challenge the law in the courts.

James Bopp, a prominent anti-gay lawyer and Terre Haute resident, helped draft the amendment. Bopp is involved in several high-profile cases involving gay rights, including a California lawsuit aimed at shielding the identities of donors to anti-gay campaigns.

Pennsylvania lawmakers are preparing to consider a similar measure. On Tuesday, Pennsylvania state Senator John H. Eichelberger Jr. introduced a joint resolution that would define marriage as a heterosexual union in the state constitution.