diff --git a/modules/sale/sale.py b/modules/sale/sale.py
index b0250121e3..e8632cd800 100644
--- a/modules/sale/sale.py
+++ b/modules/sale/sale.py
@@ -1523,7 +1523,7 @@ class SaleLine(TaxableMixin, sequence_ordered(), ModelSQL, ModelView):
         with Transaction().set_context(
                 self._get_context_sale_price()):
             unit_price = Product.get_sale_price([self.product],
-                self.quantity or 0)[self.product.id]
+                abs(self.quantity or 0))[self.product.id]
             if unit_price is not None:
                 unit_price = round_price(unit_price)
             return unit_price