Facebook narrowly missed Wall Street revenue estimates on Wednesday, reporting a profit of 42 cents per share on $3.54 billion in total revenue for the first quarter of 2015.
Wall Street estimates for the social network were profit of 40 cents per share on $3.56 billion in revenue for the quarter.
Facebook makes almost all of its revenue through advertising, and 73 percent of that ad revenue in Q1 came from mobile, the highest such percentage Facebook has ever reported.
One explanation for the revenue miss (although it’s a very narrow miss, indeed) is the change in foreign exchange rates.
Facebook COO Sheryl Sandberg spoke with Re/code shortly after market close on Wednesday and pointed out that without the exchange rate changes, ad revenue would be up 55 percent as opposed to the 46 percent increase Facebook reported.
She also added that moving forward, Facebook needs to do a better job of serving more relevant, targeted ads. (This is something Facebook says almost every quarter, and apparently remains as the company’s go-to “here’s what we can improve upon” example.)
Analysts were also looking for user growth to jump around 13 percent year-over-year, an expectation Facebook met.
The social network now has 1.44 billion monthly users, an increase of 13 percent over the same quarter last year. Included in that number are 936 million daily active users, up roughly 17 percent.
One of Facebook’s other properties, standalone messaging app WhatsApp, is also growing steadily. It announced last week that it has more than 800 million users, up from 700 million in January.
Facebook CEO Mark Zuckerberg has said in the past that the company wouldn’t look to monetize this massive user base until it hit at least one billion users. But with growth happening so quickly, that’s likely to come by the end of the year.
Still, Sandberg says that Facebook still isn’t thinking about or prepping for what a WhatsApp revenue stream might look like.
“We’re thrilled with their growth,” she said, “[but] we are not currently working on monetization for WhatsApp. We’re continuing to work on growth.”
Facebook stock is down more than 2 percent in after hours trading, but the company has its earnings call at 2 p.m. PT and you can bet it will point out the exchange rate issue early on.
This article originally appeared on Recode.net.