Nokia Oyj, the Finnish smartphone maker using Microsoft’s operating system, fell to a 16-year low after analysts said sales may be hurt as the US supplier’s new program won’t work on its current phones.

Nokia dropped 11.4 percent to 1.71 euros in Helsinki. The stock has lost more than half of its value this year. (US ADRs closed at $2.19, down 8 percent.) Microsoft has said that its Windows Phone 8 program will go on sale in the second half and that phones running previous versions can’t be upgraded.

Also yesterday, Microsoft confirmed that it has agreed to buy online social network firm Yammer for $1.2 billion.