Get space name from event listener

I’m creating an event listener to override default search behavior of Confluence.
To do that I need to identify space name from which search was initiated.

How can I achieve that within listener plugin? Things like event.getSource() give me only:
com.atlassian.confluence.plugins.cql.impl.DefaultCQLSearchService@198729b5

event.getSearchQuery().getParameters() don’t have it either