diff --git a/purchase.py b/purchase.py
index ef503e674a..d839ae069f 100644
--- a/purchase.py
+++ b/purchase.py
@@ -1772,6 +1772,7 @@ class Line(sequence_ordered(), ModelSQL, ModelView):
         default.setdefault('moves_ignored', None)
         default.setdefault('moves_recreated', None)
         default.setdefault('invoice_lines', None)
+        default.setdefault('actual_quantity')
         return super().copy(lines, default=default)