The Wall Street Journal on Sunday reported that Simon, the top U.S. mall developer and owner of many of the country’s best malls, is looking into the prospect of turning some of those stores into Amazon distribution hubs, which would aid the Internet retail giant’s shipping speed and shorten the so-called last mile in e-commerce delivery.

Amazon has about 100 fulfillment centers in the U.S. but is looking to speed up delivery with facilities closer to customers in an effort to better counter rivals like Walmart and Target, which can use 4,400 and 1,800 stores respectively to assist their e-commerce.

The companies declined to comment. But the stock market liked the prospect for Simon, sending its shares up 7% on Monday morning.

E-commerce companies have typically located fulfillment centers far from large areas to enjoy lower rent, labor, and operating costs. But with the flood of mall-based retail bankruptcies this year— J.C. Penney, Neiman Marcus, J.Crew, Ann Taylor parent Ascena Retail—on top of Sears in 2018, and big tenants like Macy’s and Nordstrom also closing stores, mall operators like Simon have little choice but to rethink their business model.

Adding to the pain, many tenants did not pay their rent during the spring’s COVID-19-related lockdowns: Gap Inc., which generates 3.5% of Simon’s rental income and is being sued by its landlord, was one such retailer.

The old model would see a department store “anchor” a mall and attract shoppers to the property in a way that would benefit all tenants, and be rewarded with very cheap rent. That drawing power has waned in the past two years. And according to estimates published by the WSJ, Amazon pays about $10 per square foot at its distribution centers, suggesting Simon would get more than what a department store can offer.

Another source of strain for Simon and its rivals: Rents across the mall are falling. According to real estate research firm Costar, mall rents will fall about 4.3% this year, after rising more than 10% in the preceding four years.

Simon, just like other mall operators, has been trying to reinvent its tenancy mix for years, adding more restaurants, movie theaters, and other entertainment options to become less reliant on department stores and apparel stores. (That effort has been slow going. This spring, Costar found that 14 of the 20 largest mall tenants across the industry remain either apparel retailers or department store chains.) 

Of course, amid the COVID-19 outbreak, turning to theaters or eateries is not going to save malls. Enter Amazon, even if that means Simon would be handing over prime real estate. (Simon sold off its weaker malls years ago, leaving it with a relatively strong portfolio that includes top centers like Roosevelt Field, Long Island.)

While exploratory for now, Simon’s tie-up with Amazon would likely irk many of its tenants, bringing the proverbial fox into the henhouse, not to mention the fact that an Amazon fulfillment center would not increase shopper visits to malls that desperately need them. And that could hurt Simon’s malls longer term.

“While it pays the rent, this is a white flag moment. Tenants surrounding the locations are going to want huge rent reductions or walk away,” Stacey Widlitz, president of SW Retail Advisors, tells Fortune. Typically, lease clauses allow a mall tenant to break a lease if the store is no longer within a certain distance of anchor stores.

Simon will report its most recent quarterly results on Monday afternoon and is expected to post its smallest quarterly profit in nearly six years, hurt by the extended store closures in April as well as tenants withholding rent. Simon is reportedly in talks to buy Penney out of bankruptcy with another mall developer, Brookfield Property Partners.