diff --git a/option.py b/option.py
index acc9079..3848850 100644
--- a/option.py
+++ b/option.py
@@ -50,15 +50,15 @@ class Option(HiddenBaseType, DisabledBaseType, ModeBaseType):
         if mode not in modes:
             raise ConfigError("mode {0} not available".format(mode))
         self.mode = mode
+        _default = default
         if default != None:
             if self.multi == True and type(default) != list:
-                _default = [default]
-            else:
-                _default = default
+                raise ConfigError("invalid default value {0} "
+                "for option {1} : not list type".format(str(default), name))
             if not self.validate(_default):
                 raise ConfigError("invalid default value {0} " 
-                                         "for option {1}".format(default, name))
-        self.default = default
+                                         "for option {1}".format(str(default), name))
+        self.default = _default
         
     def validate(self, value):
         if self.multi == False:
@@ -113,7 +113,10 @@ class Option(HiddenBaseType, DisabledBaseType, ModeBaseType):
 
         if who == "default":
             # changes the default value (and therefore resets the previous value)
-            self.default = value
+            if self._validate(value):
+                self.default = value
+            else:
+                raise ConfigError("invalid value %s for option %s" % (value, name))
         apply_requires(self, config)
         # FIXME put the validation for the multi somewhere else
 #            # it is a multi **and** it has requires