diff --git a/trytond/model/modelstorage.py b/trytond/model/modelstorage.py
index 32d6a531..e74ff841 100644
--- a/trytond/trytond/model/modelstorage.py
+++ b/trytond/trytond/model/modelstorage.py
@@ -1084,6 +1084,15 @@ class ModelStorage(Model):
                 if hasattr(field, 'selection') and field.selection:
                     if isinstance(field.selection, (tuple, list)):
                         test = set(dict(field.selection).keys())
+                        instance_sel_func = False
+                    else:
+                        sel_func = getattr(cls, field.selection)
+                        instance_sel_func = is_instance_method(cls,
+                            field.selection)
+                        if not instance_sel_func:
+                            test = sel_func()
+                            test = set(dict(test))
+
                     for record in records:
                         value = getattr(record, field_name)
                         if field._type == 'reference':
@@ -1091,12 +1100,8 @@ class ModelStorage(Model):
                                 value = value.__class__.__name__
                             elif value:
                                 value, _ = value.split(',')
-                        if not isinstance(field.selection, (tuple, list)):
-                            sel_func = getattr(cls, field.selection)
-                            if not is_instance_method(cls, field.selection):
-                                test = sel_func()
-                            else:
-                                test = sel_func(record)
+                        if instance_sel_func:
+                            test = sel_func(record)
                             test = set(dict(test))
                         # None and '' are equivalent
                         if '' in test or None in test: