Beyoncé said she is offering free lifetime tickets to any of her or Jay-Z's shows. There's only one catch -- she wants you to go vegan first.

The singer shared the news of the contest in an Instagram post promoting The Greenprint Project, which encourages people to adopt a plant-based diet to reduce their environmental footprint. The project is linked to a recently-published book by Beyoncé's trainer, Marco Borges, for which the she and Jay-Z wrote the introduction.

"The facts about plant-based eating are hard to ignore," they wrote. "The benefits of a single plant-based meal per day can have a profound impact on our health and the environment."

"Our Greenprint is the positive impact we can have on the world by eating plant-based meals," the site explains, before delving into some of the positive global effects of following a vegan diet. It highlights the environmental benefits on trees, water consumption and carbon emissions. "We each have the potential to save our planet with our meal choices," it concludes. The science supports these claims -- multiple studies have recently confirmed the need to decrease meat consumption worldwide to improve both human health and the environment.

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By sharing their "Greenprint," fans are encouraged to commit to adding at least some plant-based meals into their diets. The site provides a drop-down menu of Greenprint options, including:

All plants. All the time. Plant based for breakfast Plant based at work Two plant-based meals a day Meatless Mondays Plant-based on weekdays

Beyoncé said her Greenprints are "plant based for breakfast" and "meatless Mondays." Once a user selects their Greenprint, a graphic is presented featuring their choice to share on social media.

To enter the contest, all fans have to do is enter their name and email on the site. The winner will receive a ticket to one concert per Beyoncé or Jay-Z tour for "life," though the site specifies it's actually for a maximum of 30 years. A winner will be selected at random on May 22.

Followers of Beyoncé were immediately on board, sharing their new plant-based lifestyles on Twitter:

@Beyonce: go vegan and enter for a chance to win free tickets to my concert for life.

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Me: ... pic.twitter.com/dcXPvVKkCN — Caitlyn (@C_Swizzle_13) January 31, 2019