diff --git a/phpBB/includes/search/fulltext_postgres.php b/phpBB/includes/search/fulltext_postgres.php
index 12a1203249..34a27f294c 100644
--- a/phpBB/includes/search/fulltext_postgres.php
+++ b/phpBB/includes/search/fulltext_postgres.php
@@ -343,6 +343,12 @@ class phpbb_search_fulltext_postgres extends phpbb_search_base
 			return false;
 		}
 
+		// When search query contains queries like -foo
+		if (strpos($this->search_query, '+') === false)
+		{
+			return false;
+		}
+
 		// generate a search_key from all the options to identify the results
 		$search_key = md5(implode('#', array(
 			implode(', ', $this->split_words),