diff --git a/bom.py b/bom.py
index a7990c7..d0bcb8d 100644
--- a/bom.py
+++ b/bom.py
@@ -13,3 +13,13 @@ class BOM(metaclass=PoolMeta):
     __name__ = 'production.bom'
 
     tasks_configuration = fields.One2Many('production.configuration_task', 'ldm', 'Tasks Configuration')
+
+    @classmethod
+    def copy(cls, records, default=None):
+        if default is None:
+            default = {}
+        else:
+            default = default.copy()
+        default.setdefault('output_products', None)
+        default.setdefault('tasks_configuration', None)
+        return super(BOM, cls).copy(records, default=default)
diff --git a/product.py b/product.py
index a990567..2e386f1 100644
--- a/product.py
+++ b/product.py
@@ -21,6 +21,16 @@ class Product(metaclass=PoolMeta):
                     product_mix=len(self.products_mix), 
                     quantity=self.quantity_mix_required))
 
+    @classmethod
+    def copy(cls, records, default=None):
+        if default is None:
+            default = {}
+        else:
+            default = default.copy()
+        default.setdefault('tasks', None)
+        return super(Product, cls).copy(records, default=default)
+
+
 class ProductMixOption(ModelSQL):
     'Product Mix Option'
     __name__ = 'product.product-mix.option'