diff --git a/modules/sale_supply/purchase.py b/modules/sale_supply/purchase.py
index 9984f39cb7..2b7d11ed37 100644
--- a/modules/sale_supply/purchase.py
+++ b/modules/sale_supply/purchase.py
@@ -31,6 +31,12 @@ class Request(metaclass=PoolMeta):
                     queue_batch=context.get('queue_batch', True)):
                 Sale.__queue__.process(Sale.browse(sales))
 
+    @classmethod
+    def copy(cls, requests, default=None):
+        default = default.copy() if default is not None else {}
+        default.setdefault('sale_lines')
+        return super().copy(requests, default=default)
+
     @classmethod
     def delete(cls, requests):
         pool = Pool()