OpenSearch omnibox not working

I added the following link tag to my head section in index.html:

<link href="/opensearch.xml" title="Ptakopět" rel="search" type="application/opensearchdescription+xml"> 

opensearch.xml contains:

<OpenSearchDescription xmlns="http://a9.com/-/spec/opensearch/1.1/">     <ShortName>Ptakopět</ShortName>     <Description>Translate with Ptakopět.</Description>     <Url template="https://ptakopet.vilda.net/?q={searchTerms}" type="text/html" method="get"/>     <Image width="16" height="16">/img/icon.png</Image> </OpenSearchDescription> 

My goal is to add the Tab to search functionality to the address bar, but the browser (Chrome) does not seem to pick up the opensearch.xml settings properly (pressing tab just skips to the next result in address bar).

Is there some obvious error or at least some way to debug/bisect why is it not working?