diff --git a/tiramisu/error.py b/tiramisu/error.py
index 1fb3b6a..e167413 100644
--- a/tiramisu/error.py
+++ b/tiramisu/error.py
@@ -159,11 +159,13 @@ class _CommonError:
                  val,
                  display_type,
                  opt,
-                 err_msg):
+                 err_msg,
+                 index):
         self.val = val
         self.display_type = display_type
         self.opt = weakref.ref(opt)
         self.err_msg = err_msg
+        self.index = index
         super().__init__(self.err_msg)
 
     def __str__(self):
diff --git a/tiramisu/option/option.py b/tiramisu/option/option.py
index fae71a2..a04c96e 100644
--- a/tiramisu/option/option.py
+++ b/tiramisu/option/option.py
@@ -302,13 +302,15 @@ class Option(BaseOption):
                             warnings.warn_explicit(ValueWarning(_value,
                                                                 self._display_name,
                                                                 self,
-                                                                err_msg = '{0}'.format(err)),
+                                                                '{0}'.format(err),
+                                                                _index),
                                                    ValueWarning,
                                                    self.__class__.__name__, 0)
                         else:
                             raise err
         try:
             val = value
+            err_index = force_index
             if not self.impl_is_multi():
                 do_validation(val, None)
             elif force_index is not None:
@@ -316,7 +318,7 @@ class Option(BaseOption):
                     if not isinstance(value, list):
                         raise ValueError(_('which must be a list'))
                     _is_not_unique(value)
-                    for idx, val in enumerate(value):
+                    for val in value:
                         do_validation(val,
                                       force_index)
                 else:
@@ -325,19 +327,19 @@ class Option(BaseOption):
             elif not isinstance(value, list):
                 raise ValueError(_('which must be a list'))
             elif self.impl_is_submulti():
-                for idx, lval in enumerate(value):
+                for err_index, lval in enumerate(value):
                     _is_not_unique(lval)
                     if not isinstance(lval, list):
                         raise ValueError(_('which "{}" must be a list of list'
                                            '').format(lval))
                     for val in lval:
                         do_validation(val,
-                                      idx)
+                                      err_index)
             else:
                 _is_not_unique(value)
-                for idx, val in enumerate(value):
+                for err_index, val in enumerate(value):
                     do_validation(val,
-                                  idx)
+                                  err_index)
 
             if not is_warnings_only or not check_error:
                 self.valid_consistency(option_bag,
@@ -350,11 +352,13 @@ class Option(BaseOption):
                 raise ValueOptionError(val,
                                        self._display_name,
                                        option_bag.ori_option,
-                                       '{0}'.format(err))
+                                       '{0}'.format(err),
+                                       err_index)
             warnings.warn_explicit(ValueErrorWarning(val,
                                                     self._display_name,
                                                     option_bag.ori_option,
-                                                    '{0}'.format(err)),
+                                                    '{0}'.format(err),
+                                                    err_index),
                                    ValueErrorWarning,
                                    self.__class__.__name__, 0)
 
@@ -635,7 +639,8 @@ class Option(BaseOption):
                 warnings.warn_explicit(ValueWarning(value,
                                                     self._display_name,
                                                     current_opt,
-                                                    "{}".format(err)),
+                                                    "{}".format(err),
+                                                    option_bag.index),
                                        ValueWarning,
                                        self.__class__.__name__, 0)
             else: