Index: branches/5.2.x/core/units/helpers/priority_helper.php
===================================================================
--- branches/5.2.x/core/units/helpers/priority_helper.php
+++ branches/5.2.x/core/units/helpers/priority_helper.php
@@ -51,7 +51,7 @@
 			$items_count = $this->Conn->GetOne($sql);
 			$current_priority = $object instanceof kDBList ? 0 : $object->GetDBField('Priority');
 
-			if ( $is_new || $current_priority == -($items_count + 1) ) {
+			if ( $is_new || $current_priority == -($items_count + 1) || $this->isTempTableOnly($object) ) {
 				$items_count++;
 			}
 
@@ -73,6 +73,22 @@
 		}
 
 		/**
+		 * Determines if an item only exists in temp table.
+		 *
+		 * @param kDBBase $object Object.
+		 *
+		 * @return boolean
+		 */
+		protected function isTempTableOnly(kDBBase $object)
+		{
+			if ( !$object->IsTempTable() || ($object instanceof kDBList) ) {
+				return false;
+			}
+
+			return $object->GetID() <= 0;
+		}
+
+		/**
 		 * Updates priorities for changed items
 		 *
 		 * @param kEvent $event