When men go shopping at Old Navy, it doesn’t matter what size they buy; prices don’t vary. But that’s not the same for women, who may have to pay extra if they purchase plus-size items. In just a few days, nearly 19,000 people have petitioned the retailer asking it to end this policy, but Old Navy claims there is a reason that it charges more for larger female sizes.

The Change.org petition was started late last week after its creator noticed that plus-size jeans at Old Navy were selling for upwards of $15 more per pair than the smaller sizes. Meanwhile, men’s jeans were the same price regardless of size.

“I was fine paying the extra money as a plus-sized woman, because, you know, more fabric equals higher cost of manufacture,” writes the petitioner. “However, selling jeans to larger-sized men at the same cost as they sell to smaller men not only negates the cost of manufacture argument, but indicates that Old Navy is participating in both sexism and sizeism, directed only at women.”

Additionally, the petition points out that there is a “Women’s Plus” section at Old Navy but no equivalent in men’s apparel.

We reached out to Old Navy parent company Gap Inc., where a rep for the company told us the retail giant has a reason for charging more for the plus-size women’s items.

The rep explains that while men’s bigger sizes are merely larger versions of the same clothing, Old Navy puts in additional work behind the scenes for women’s clothing.

“They are created by a team of designers who are experts in creating the most flattering and on-trend plus styles,” says the rep in an e-mail to Consumerist, “which includes curve-enhancing and curve-flattering elements such as four-way stretch materials and contoured waistbands, which most men’s garments do not include. This higher price point reflects the selection of unique fabrics and design elements.”

UPDATE: After seeing Old Navy’s statement, petitioner Renee Posey tells Consumerist that the company is trying to “obfuscate the truth, appease the plus-sized female consumer, and frankly make this whole thing go away.”

She claims that the “curve-enhancing” and “curve-flattering” design elements, like contoured waistbands and and four-way stretch materials, are also included in Old Navy’s regular women’s line.

“So the implication that these elements are something extra not included in their regular line, and thus worthy of the up-charge, is blatantly false,” writes Posey.

She also questions Old Navy’s investment in a special design team for its plus-size products, as there are fewer options for larger sizes. Posey claims, for example, that the regular women’s size range offers 161 choices of coats while the “Women’s Plus” only offers 32 options.

“Overall, their assertion that the higher price reflects the ‘selection of unique fabrics and design elements’ falls flat,” writes Posey. “They have been called out on unfair pricing practices and they’re simply trying to spin it back in their direction so they can maintain incredibly high profit margins by keeping up business as usual.”

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