Amazon announced plans to lower its Prime membership fee for low-income Americans in a bid to tap into one of Walmart’s largest customer pools.

The king of e-commerce said it will offer people who obtain government assistance a $5.99 monthly Prime membership rate rather than the typical $10.99/month or $99 annual fee, the Wall Street Journal reports. The move could threaten Walmart, which relies on low-income consumers and made around $13B in sales last year from customers using the Supplemental Nutrition Assistance Program.

An Amazon spokeswoman said the company will require participants to show cards typically used for food stamps to prove eligibility, and Amazon will confirm eligibility every year for up to four years. Low-income shoppers are a big opportunity for online retailers, but consumers who lack bank accounts or credit cards still face challenges buying online.