diff --git a/trytond/trytond/model/fields/function.py b/trytond/trytond/model/fields/function.py
index 6b2c0eb04d..a9805233b1 100644
--- a/trytond/trytond/model/fields/function.py
+++ b/trytond/trytond/model/fields/function.py
@@ -41,7 +41,7 @@ class Function(Field):
             ``lazy`` or ``eager``.
         '''
         assert isinstance(field, Field)
-        self._field = field
+        self._field = copy.deepcopy(field)
         self._type = field._type
         self.getter = getter
         self.getter_with_context = getter_with_context