diff --git a/tryton/gui/window/view_form/screen/screen.py b/tryton/gui/window/view_form/screen/screen.py
index 3e5a7455b4..b290951e40 100644
--- a/tryton/gui/window/view_form/screen/screen.py
+++ b/tryton/gui/window/view_form/screen/screen.py
@@ -140,7 +140,7 @@ class Screen(SignalEvent):
                         ):
                     if name not in fields:
                         fields[name] = {
-                            'string': string,
+                            'string': string.decode('utf-8'),
                             'name': name,
                             'type': type_,
                             }