(CNN) A woman in Texas was sentenced Wednesday to a five-year prison term for voting illegally in the 2016 presidential election while on supervised release for a tax fraud conviction.

When she voted in the 2016 election, Crystal Mason had already served almost three years in prison for her fraud conviction but had not yet completed her sentence and was still serving a three-year supervised release period, according to the Fort Worth Star-Telegram.

Mason reportedly told the court, however, that she was not aware of that prohibition and had not been informed that she was ineligible to vote until her sentence was complete.

"She voted in good faith," Mason's defense attorney J. Warren St. John said in an interview. "I don't think she should be going to prison for that." Her attorney has already filed an appeal. "I think Texas law is extreme in terms of sentencing people to prison for voting violations," he said.

Mason signed an affidavit in order to cast a provisional ballot, which stated that it is a violation of the law to vote if you are a convicted felon, but Mason did not see that part of the ballot, St. John said.

"Ms. Mason was never asked if she was a convicted felon by the election judge nor did she indicate that she was a convicted felon," her attorney said. "Ms. Mason voted in good faith that she could legally vote because she was never notified by any government agency that it was against the law to vote."

Prosecutors argued that Mason either intended to vote illegally or should have been aware that she was not eligible to vote, according to The Fort Worth Star-Telegram.

"There were multiple safeguards in place to keep Crystal Mason from breaking the law, but she still made that choice," Tarrant County Criminal District Attorney Sharen Wilson said a statement.

"She signed and affirmed a document which clearly stated that (1) she was prohibited from voting due to her status as a convicted felon still serving her term of supervision, and (2) she would be committing a second degree felony if she lied about her status," Wilson said. "The judge found her guilty of illegal voting beyond a reasonable doubt."

The Star-Telegram reported at the time of her indictment that Mason believed she was being targeted for her vote -- which she said she cast for Democratic nominee Hillary Clinton.