Even without a Prime membership, Amazon always offered free (and slow) shipping for orders over a certain minimum. For the longest time, that minimum was $25, but in 2013, the company raised it to $35. In its latest move to push its $99/year Prime membership with free two-day shipping, though, the company has now quietly raised this limit to $49.

The good news: If you’re buying books, the minimum to qualify for free shipping is still $25 (assuming those books are eligible for the free shipping promotion).

With this move, Amazon is obviously trying to push more of its customers to subscribe to its Prime service. With its two-day service (or even one-hour delivery for those who can get Prime Now), Prime offers significantly faster delivery and lots of other perks. And now that it takes $50 before you get free shipping, Prime probably looks like a worthwhile expense to more people.

For Amazon, this move also means that it may be able to cut its shipping cost down a bit and increase its profit margins. In its last earnings release, Amazon said its fulfillment costs were up 32.8 percent year-over-year. That’s partly due to the expansion of its Prime Now service, but if Amazon can convince people to spend more per order, pay regular shipping costs, or sign up for Prime, that surely isn’t going to hurt its bottom line.