On Thursday, Amazon said that first quarter revenue from Amazon Prime rose 49% to $1.9 billion compared to the same period a year earlier.

Amazon Prime (AMZN) has become an important pillar in Amazon’s e-commerce and streaming businesses. For $99 annually, Amazon Prime members can stream digital movies, TV shows, podcasts, and Amazon’s original productions in addition to getting free two-day shipping and one-hour delivery on certain orders. Prime is used by the company to encourage loyalty with shoppers who want to access faster shipping on items like toilet paper or coffee or toys.

Get Data Sheet, Fortune’s technology newsletter.

Amazon only recently started to provide details about the revenue it collects from Prime subscriptions. Amazon’s chief financial officer Brian Olsavsky clarified on the earnings call on Wednesday that the segment reported as “retail subscription services” includes Prime as well as other subscriptions services, like those for podcasts. But it is believed that the bulk of this segment’s revenue comes from Prime subscriptions.

For more on Amazon, watch:

Amazon continues to try to add more benefits to Prime subscribers. Last year, Amazon added audiobooks and podcasts to Prime, and has offered exclusive discounts on other services such as music streaming for its members.

Earlier this week, research firm Consumer Intelligence Research Partners reported that Prime had doubled in size over the past two years to 80 million members. Amazon did not disclose any updated Prime numbers on Thursday.

Revenue coming directly from Prime remains a small part of Amazon’s overall business.

In the first quarter, the company’s said its overall sales grew 23% to $35.7 billion, slightly edging out analyst expectations of $35.3 billion. Profits rose 41% to $724 million from the same quarter in 2016.

Buoyed by the strong earnings report, Amazon’s shares rose 3.6% in after hours trading to $951.45.