A small move from Google has apparently caused big trouble for Bankrate.

Google, now a subsidiary of Alphabet, announced this week that it was shuttering Compare, its service for users deciding between various mortgage, insurance, and credit card offers. You’d think this would be good news for Bankrate, a site that lets users, uh, decide between various mortgage, insurance, and credit card offers.

Not so. Bankrate [Ticker: RATE] stock tumbled $5.88, or 46%, in early trading Thursday. Bankrate went public in 2011 at around $15 per share.

Yesterday, on the company’s Q4 earnings call, President & CEO Kenneth Esterow noted “two issues that emerged in Q4 2015 that impacted our results”:

First, as Q4 progressed, Google began testing a much more prominent version of its Compare credit card offering and also increased how frequently this new format appeared on Google searches relating to credit cards. Second, many Bankrate.com deposit advertisers reduced their ad budgets in the quarter. With respect to cards in the quarter, Google tried testing a different visual layout of their Compare credit card unit that switched from horizontal, where it takes up the equivalent of one paid advertiser position, to vertical, where it showed a stack of credit card offers from many credit card related searches. Now the practical impact of this test was that consumers searching Google for credit cards often saw Google’s own marketplace, not only first, but also more prominently and more frequently.

Bankrate — and many other comparison services, such as Lending Tree — should expect some tailwinds from Google’s decision to shutter Compare, but Google’s search is also instrumental to Bankrate’s business, and a simple change in ad layouts has seemingly proved ruinous. Revenue at RATE declined about 8% last quarter, the company announced. The decline in deposit advertisers mentioned above, for example, was not elaborated upon during the call, though plans for improving the situation were laid out.

“In 2016, we will overhaul Bankrate.com to provide an even more compelling site and personalized consumer experience with a full site redesign,” Esterow said. “We’re also providing more sophisticated tools for RATE’s advertisers to improve their ROI and for us to capture a greater share of their spend.”

The importance of search is supposed to be on the decline with the advent of mobile, but many businesses are still search-dependent, and the smallest moves from Google can shake them up considerably. As Bankrate now knows well.