diff --git a/modules/purchase_trade/fee.py b/modules/purchase_trade/fee.py
index 31c8cb0..44914cd 100755
--- a/modules/purchase_trade/fee.py
+++ b/modules/purchase_trade/fee.py
@@ -262,7 +262,7 @@ class Fee(ModelSQL,ModelView):
         elif self.mode == 'ppack':
             unit  = self.get_unit()
             if unit and self.unit:
-                return self.price / self.unit.factor * unit.factor
+                return self.price / Decimal(self.unit.factor) * Decimal(unit.factor)
         elif self.mode == 'pprice' or self.mode == 'pcost':
             if self.line and self.price:
                 return round(self.price * Decimal(self.line.unit_price) / 100,4)