A new limited edition “Forever” stamp issued Tuesday by the U.S. Postal Service to honor the late poet, author and civil rights activist Maya Angelou carries a quote that has been attributed to someone else.

The stamp dedicated at a Washington ceremony showcases Atlanta artist Ross Rossin’s 2013 portrait of Angelou. The stamp includes the quotation: "A bird doesn’t sing because it has an answer, it sings because it has a song.”

However, the inspirational quote cannot be found in any of Angelou’s works. Instead, it came from author Joan Walsh Anglund.

The children’s book author told The Washington Post the quotation is from her book of poems “A Cup of Sun,” published in 1967. Anglund said she didn’t know about the stamp, but hopes that it is successful.

"It's an interesting connection, and interesting it would happen and already be printed and on her stamp," Anglund said. "I love her and all she's done."

The quote has been attributed to Angelou before. Last year, while presenting the National Medal of the Arts and Humanities, President Obama attributed the quote to Angelou while honoring other artists.

Postal Service spokesman David Partenheimer said Tuesday that the quotation was included because it's something Angelou referenced frequently.

"Maya Angelou cited this sentence frequently in media interviews and other forums and it provides a connection to her first memoir 'I Know Why the Caged Bird Sings,'" he said. "The sentence was chosen to accompany her image on the stamp to reflect her passion for the written and spoken word. The sentence held great meaning for her and she is publicly identified with its popularity."

Ethel Kessler of Bethesda, Maryland, designed the stamp based on Rossin's portrait, the postal service said.

Angelou rose from poverty, segregation and violence to become a force on stage, screen and the printed page. She died last May at her Winston-Salem, North Carolina, home at 86.

The Associated Press contributed to this report.