Reproduced with Nightly 42.0a1 2015-07-26 under Win 7 64-bit, Ubuntu 12.04 LTS 32-bit and Mac OS X 10.9.5. Steps to reproduce: 1. Make sure Yahoo is set as the default search engine 2. Enter some text in the awesome bar and navigate to search suggestions using keyboard arrows - press Enter 3. In a new tab, enter text in awesome bar and click on a search suggestion 4. Notice the Yahoo links opened at steps 2 & 3 Actual results: Url is redirected to https://us.search.yahoo.com/search?fr=yhs-invalid&p=text Expected results: https://search.yahoo.com/yhs/search?p=text&ei=UTF-8&hspart=mozilla&hsimp=yhs-002 is the correct url. This doesn't reproduce when the search is performed directly from awesome bar (enter text and press Enter or click "Go to the address in the Location Bar"). Notes: I tried to find the regression range by modifying the pref unifiedautocomplete to true and this is the result: Last good revision: 34a66aaaca81 (2015-02-05) First bad revision: 7c5f187b65bf (2015-02-06) Pushlog: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=34a66aaaca81&tocha nge=7c5f187b65bf It seem to be regressed by bug 1126551.