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Colorado voters are heading to the polls next month to decide whether to remove or keep slavery in the state’s constitution.

Slavery is still technically legal in a handful of U.S. states, including Colorado, Nevada, North Carolina, Tennessee and Wisconsin, and in the U.S. Constitution under the 13th amendment.

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Article II, Section 26 of Colorado’s constitution reads that there, “shall never be in this state either slavery or involuntary servitude, except as a punishment for crime, whereof the party shall have been duly convicted.”

A close-up of an 1876 copy of the Colorado Constitution which contains an exception under which slavery could be used as punishment for a crime, at the Stephen H. Hart Library & Research Center in Denver. Colorado. AP Photo/P. Solomon Banda

Colorado legislators want to change the wording of the constitution. And that is what residents will be voting about on Nov. 6.

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Amendment A will change the wording to, “There shall never be in this state either slavery or involuntary servitude.”

In 2016, Colorado voters almost passed the amendment. However, the wording was so confusing that many people weren’t sure whether they were voting for or against slavery, according to ACLU Colorado.

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The 2016 measure was titled, “End Exception to Involuntary Servitude Prohibition,” while this year it has a more straightforward title, “Prohibit Slavery and Involuntary Servitude in All Circumstances.”

Proponents of the change, including Abolish Slavery Colorado, argue the constitution should be updated because it represents a time when not all people were seen as human beings or treated with dignity.

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Opponents said the change could result in legal uncertainty around current prisoner work practices in the state, according to Colorado Public News.

“Colorado voters have the opportunity on November 6 to vote yes on Amendment A and close this constitutional loophole, finishing the constitutional abolition of slavery in Colorado,” Nathan Woodliff-Stanley with ACLU Colorado said.

Slavery still in the U.S. Constitution?

Like Colorado, the U.S. Constitution (and 15 other states) allow slavery as punishment for a crime.

It states: “Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.”

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According to ACLU Colorado, after the Civil War in 1865, the 13th Amendment abolished slavery. However, in order to get it approved, the amendment was modified to say, “except as a punishment for crime whereof the party shall have been duly convicted.”

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While some states do not have language and some explicitly prohibit slavery with no exceptions, the Colorado constitution uses the same exception allowing slavery as a punishment for crime, according to the ACLU.