Yahoo’s recent increase in the U.S. desktop search share has started to falter, according to comScore’s monthly qSearch analysis.

In December, Yahoo replaced Google as the default search engine on Mozilla Firefox. That month, the first in the five-year partnership, Yahoo saw its highest share – 11.8 percent – of the desktop search market since 2009. The number increased to 13 percent in January, before starting to decline.

In February, Yahoo’s share went down to 12.8 percent, with those 0.2 percentage points dividing between Google and Microsoft. Google continues to have the lion’s share of the search market; even with Yahoo’s comeback, Google never dipped below 64 percent.

The qSearch analysis comes from 17 billion searches. In February, about 11 billion of those searches – or 64.5 percent – were Google. Microsoft’s share accounted for 19.8 percent, or 3.4 billion searches.

comScore also looked at Ask Network and AOL, which remained the same from month to month, at 1.8 percent and 1.1 percent, respectively.