After a sluggish first quarter for retailers, retail sales ticked up 4.5% year over year in April, led by an 11.9% gain in nonstore sales, the U.S. Commerce Department reported today.

Nonstore sales adjusted for seasonal variations totaled $51.351 billion, up 11.9% from $45.889 billion in April 2016 and 1.4% from $50.642 billion in March. Nonstore sales had grown 11.4% in March 2017 over March 2016.

Nonstore sales mainly take place online. But they are an imperfect indicator of e-commerce growth because they also include mail and telephone orders, door-to-door sales and sales by home heating oil companies. The Commerce Department will release its first quarter e-commerce report Tuesday. Online retail sales increased 15.6% in 2016 over 2015, according to the Commerce Department.

For the first four months of 2017, nonstore sales were up 10.7% over the same period in 2016 while total retail sales were ahead 3.5%. The 4.5% growth in April was a significant increase from the first quarter, when adjusted retail sales increased only 3.2% year over year.