This Thursday, Oct. 17, 2019 photo shows the exterior of a McDonald's restaurant in Mebane, N.C. McDonald's reports financial earns on Tuesday, Oct. 22. (Photo: AP)

Surging demand for delivery is pushing comparable-store sales higher at McDonald’s, but it’s coming at a cost.

Quarterly earnings at the Chicago company were flat at $2.11 per share. Wall Street was looking for per-share earnings of $2.21, according to FactSet.

The company’s shares were down 4% in premarket trading Tuesday.

The burger giant said global sales rose 5.9% at restaurants open at least 13 months. That was better than the 5.4% increase analysts were expecting, according to a survey by FactSet. In the US, comp sales were up 4.8%.

Just over half of McDonald’s Corp. restaurants offer delivery and it’s dropping off orders to more than a million customers each day. The company partnered with DoorDash in the quarter to make deliveries in the US.

But it’s been costly to promote those efforts. McDonald’s is also undergoing expensive store renovations, in part to have dedicated delivery and mobile ordering spaces.

McDonald’s is also investing heavily in new technology to provide faster service. Last month, it acquired a Silicon Valley voice recognition startup called Apprente, with an eye toward using it to take orders at drive-thru windows. And earlier this year it bought Dynamic Yield, a startup that will help it provide customized recommendations at drivethru windows based on things like weather and restaurant traffic.

Third-quarter revenue was $5.4 billion, the company said Tuesday, just shy of Wall Street’s forecast of $5.49 billion.