diff --git a/addons/stock/stock.py b/addons/stock/stock.py
index 4059565680d..251d157dcc0 100644
--- a/addons/stock/stock.py
+++ b/addons/stock/stock.py
@@ -3002,7 +3002,7 @@ class stock_inventory_line(osv.osv):
         if res:
             location = self.pool['stock.location'].browse(cr, uid, values.get('location_id'), context=context)
             product = product_obj.browse(cr, uid, values.get('product_id'), context=context)
-            raise Warning(_("You cannot have two inventory adjustements in state 'in Progess' with the same product(%s), same location(%s), same package, same owner and same lot. Please first validate the first inventory adjustement with this product before creating another one.") % (product.name, location.name))
+            raise UserError(_("You cannot have two inventory adjustements in state 'in Progess' with the same product(%s), same location(%s), same package, same owner and same lot. Please first validate the first inventory adjustement with this product before creating another one.") % (product.name, location.name))
         if 'product_id' in values and not 'product_uom_id' in values:
             values['product_uom_id'] = product_obj.browse(cr, uid, values.get('product_id'), context=context).uom_id.id
         return super(stock_inventory_line, self).create(cr, uid, values, context=context)