diff --git a/tryton/gui/window/view_form/view/form_gtk/char.py b/tryton/gui/window/view_form/view/form_gtk/char.py
index 03f87f62ec..75c9eefcdf 100644
--- a/tryton/gui/window/view_form/view/form_gtk/char.py
+++ b/tryton/gui/window/view_form/view/form_gtk/char.py
@@ -51,8 +51,10 @@ class Char(WidgetInterface, TranslateMixin):
     def translate_widget(self):
         entry = gtk.Entry()
         entry.set_property('activates_default', True)
-        entry.set_width_chars(int(self.attrs.get('size', -1)))
-        entry.set_max_length(int(self.attrs.get('size', 0)))
+        if self.record:
+            field_size = self.record.expr_eval(self.attrs.get('size'))
+            entry.set_width_chars(field_size or -1)
+            entry.set_max_length(field_size or 0)
         return entry
 
     @staticmethod