diff --git a/htdocs/knowledgemanagement/knowledgerecord_list.php b/htdocs/knowledgemanagement/knowledgerecord_list.php
index cafb5776cf7..c4b6eb7eaa6 100644
--- a/htdocs/knowledgemanagement/knowledgerecord_list.php
+++ b/htdocs/knowledgemanagement/knowledgerecord_list.php
@@ -293,7 +293,7 @@ if (!empty($searchCategoryKnowledgemanagementList)) {
 		if (intval($searchCategoryKnowledgemanagement) == -2) {
 			$searchCategoryKnowledgemanagementSqlList[] = "NOT EXISTS (SELECT ck.fk_knowledgemanagement FROM ".MAIN_DB_PREFIX."categorie_knowledgemanagement as ck WHERE t.rowid = ck.fk_knowledgemanagement)";
 		} elseif (intval($searchCategoryKnowledgemanagement) > 0) {
-			if ($searchCategoryKnowledgemanagementOperator == 0) {
+			if (empty($searchCategoryKnowledgemanagementOperator)) {
 				$searchCategoryKnowledgemanagementSqlList[] = " EXISTS (SELECT ck.fk_knowledgemanagement FROM ".MAIN_DB_PREFIX."categorie_knowledgemanagement as ck WHERE t.rowid = ck.fk_knowledgemanagement AND ck.fk_categorie = ".((int) $searchCategoryKnowledgemanagement).")";
 			} else {
 				$listofcategoryid .= ($listofcategoryid ? ', ' : '') .((int) $searchCategoryKnowledgemanagement);