diff --git a/module/task/model.php b/module/task/model.php
index 565eedc1f5..7bd9bf250d 100644
--- a/module/task/model.php
+++ b/module/task/model.php
@@ -413,6 +413,7 @@ class taskModel extends model
         if($parentID <= 0) return true;
 
         $oldParentTask = $this->dao->select('*')->from(TABLE_TASK)->where('id')->eq($parentID)->fetch();
+        if($oldParentTask->parent != '-1') $this->dao->update(TABLE_TASK)->set('parent')->eq('-1')->where('id')->eq($parentID)->exec(); 
         $this->computeWorkingHours($parentID);
 
         $childrenStatus       = $this->dao->select('id,status')->from(TABLE_TASK)->where('parent')->eq($parentID)->andWhere('deleted')->eq(0)->fetchPairs('status', 'status');