diff --git a/inc/knowbase.class.php b/inc/knowbase.class.php
index 71999a0c0..9f83bffb6 100644
--- a/inc/knowbase.class.php
+++ b/inc/knowbase.class.php
@@ -105,20 +105,19 @@ public static function getCategoryTree() {
             [
                'SELECT' => ['COUNT DISTINCT' => KnowbaseItem::getTableField('id') . ' as cpt'],
                'FROM'   => KnowbaseItem::getTable(),
-               'LEFT JOIN' => [
+               'INNER JOIN' => [
                   KnowbaseItem_KnowbaseItemCategory::getTable() => [
                      'FKEY' => [
                            KnowbaseItem::getTable() => 'id',
                            KnowbaseItem_KnowbaseItemCategory::getTable() => KnowbaseItem::getForeignKeyField(),
                      ],
                   ],
-                  KnowbaseItemCategory::getTable() => [
-                     'FKEY' => [
-                        KnowbaseItem_KnowbaseItemCategory::getTable() => KnowbaseItemCategory::getForeignKeyField(),
-                        KnowbaseItemCategory::getTable() => 'id',
-                     ],
-                  ],
                ],
+               'WHERE'  => [
+                  KnowbaseItem_KnowbaseItemCategory::getTableField($cat_fk) => new QueryExpression(
+                      $DB->quoteName(KnowbaseItemCategory::getTableField('id'))
+                  ),
+               ]
             ],
             $kbitem_visibility_crit
          ),
@@ -230,4 +229,4 @@ public static function getFaqItems($rootCategory = 0, $keywords = '') {
 
       return ['default' => [], 'forms' => $formList];
    }
-}
\ No newline at end of file
+}