diff --git a/tryton/gui/window/view_form/model/field.py b/tryton/gui/window/view_form/model/field.py
index 7f4d066cde..b7f4e3a628 100644
--- a/tryton/gui/window/view_form/model/field.py
+++ b/tryton/gui/window/view_form/model/field.py
@@ -445,6 +445,8 @@ class O2MField(CharField):
         super(O2MField, self).state_set(model, values=values)
         if self.get_state_attrs(model).get('readonly', False):
             model.value[self.name].readonly = True
+        else:
+            model.value[self.name].readonly = False
 
 
 class ReferenceField(CharField):