diff --git a/trytond/model/modelstorage.py b/trytond/model/modelstorage.py
index 9aa0c3cd5c..f82c074ab2 100644
--- a/trytond/model/modelstorage.py
+++ b/trytond/model/modelstorage.py
@@ -1062,7 +1062,7 @@ class ModelStorage(Model):
                 def required_test(value, field_name):
                     if (isinstance(value,
                                 (BrowseRecordNull, type(None), type(False),
-                                    BrowseRecordList))
+                                    BrowseRecordList, basestring))
                             and not value):
                         self.raise_user_error('required_validation_record',
                             error_args=self._get_error_args(field_name))
diff --git a/trytond/tests/test_fields.py b/trytond/tests/test_fields.py
index 1f6d118aed..e20bd06f53 100644
--- a/trytond/tests/test_fields.py
+++ b/trytond/tests/test_fields.py
@@ -1040,6 +1040,11 @@ class FieldsTestCase(unittest.TestCase):
             self.failUnlessRaises(Exception, self.char_required.create, {})
             transaction.cursor.rollback()
 
+            self.failUnlessRaises(Exception, self.char_required.create, {
+                    'char': '',
+                    })
+            transaction.cursor.rollback()
+
             char5_id = self.char_required.create({
                 'char': 'Test',
                 })