diff --git a/product_configurator/demo/product_attribute.xml b/product_configurator/demo/product_attribute.xml
index 5e833da0..4b69d8da 100644
--- a/product_configurator/demo/product_attribute.xml
+++ b/product_configurator/demo/product_attribute.xml
@@ -335,7 +335,7 @@
                 ref('product_configurator.product_attribute_value_tow_hook'),
                 ]
             )]"/>
-            <field name="required" eval="True"/>
+            <field name="required" eval="False"/>
             <field name="multi" eval="True"/>
         </record>
 
diff --git a/product_configurator/demo/product_config_lines.xml b/product_configurator/demo/product_config_lines.xml
index 84d54ff1..0e4f7b24 100644
--- a/product_configurator/demo/product_config_lines.xml
+++ b/product_configurator/demo/product_config_lines.xml
@@ -11,6 +11,7 @@
                 ref('product_attribute_value_m235i'),
                 ref('product_attribute_value_m235i_xdrive')])]"/>
             <field name="domain_id" ref="product_config_domain_gasoline"/>
+            <field name="rule_description">Gasoline Fuel requires a Gasoline Engine to be selected</field>
         </record>
 
         <record id="product_config_line_diesel_engines" model="product.config.line">
@@ -22,6 +23,7 @@
               ref('product_attribute_value_220d_xdrive'),
               ref('product_attribute_value_225d')])]"/>
             <field name="domain_id" ref="product_config_domain_diesel"/>
+            <field name="rule_description">Diesel Fuel requires a Diesel Engine to be selected</field>
         </record>
 
         <record id="product_config_line_218_lines" model="product.config.line">
@@ -31,6 +33,7 @@
               ref('product_attribute_value_sport_line'),
               ref('product_attribute_value_luxury_line')])]"/>
             <field name="domain_id" ref="product_config_domain_218_engine"/>
+            <field name="rule_description">218i Engine has a limited selection of Lines</field>
         </record>
 
         <record id="product_config_line_luxury_lines" model="product.config.line">
diff --git a/product_configurator/models/product.py b/product_configurator/models/product.py
index 9a6bfe56..56cdd063 100644
--- a/product_configurator/models/product.py
+++ b/product_configurator/models/product.py
@@ -357,7 +357,8 @@ def create_get_variant(self, value_ids, custom_values=None):
         """
         if custom_values is None:
             custom_values = {}
-        valid = self.validate_configuration(value_ids, custom_values)
+        valid = self.validate_configuration(value_ids, custom_values,
+                                            do_raise=True)
         if not valid:
             raise ValidationError(_('Invalid Configuration'))
 
@@ -413,7 +414,7 @@ def validate_domains_against_sels(self, domains, sel_val_ids):
         return avail
 
     @api.multi
-    def values_available(self, attr_val_ids, sel_val_ids):
+    def values_available(self, attr_val_ids, sel_val_ids, do_raise=False):
         """Determines whether the attr_values from the product_template
         are available for selection given the configuration ids and the
         dependencies set on the product template
@@ -421,6 +422,7 @@ def values_available(self, attr_val_ids, sel_val_ids):
         :param attr_val_ids: list of attribute value ids to check for
                              availability
         :param sel_val_ids: list of attribute value ids already selected
+        :param do_raise: boolean on whether to raise a warning or just fail
 
         :returns: list of available attribute values
         """
@@ -436,11 +438,23 @@ def values_available(self, attr_val_ids, sel_val_ids):
             avail = self.validate_domains_against_sels(domains, sel_val_ids)
             if avail:
                 avail_val_ids.append(attr_val_id)
-
+            elif do_raise:
+                if len(config_lines) == 1 and config_lines[0].rule_description:
+                    raise ValidationError(config_lines[0].rule_description)
+                else:
+                    attribute_value = \
+                        self.env['product.attribute.value'].browse(attr_val_id)
+                    raise ValidationError(
+                        _('%s for %s is not valid in this configuration') %
+                        (attribute_value.name,
+                         attribute_value.attribute_id.name
+                         )
+                        )
         return avail_val_ids
 
     @api.multi
-    def validate_configuration(self, value_ids, custom_vals=None, final=True):
+    def validate_configuration(self, value_ids,
+                               custom_vals=None, final=True, do_raise=False):
         """ Verifies if the configuration values passed via value_ids and custom_vals
         are valid
 
@@ -448,12 +462,12 @@ def validate_configuration(self, value_ids, custom_vals=None, final=True):
         :param custom_vals: custom values dict {attr_id: custom_val}
         :param final: boolean marker to check required attributes.
                       pass false to check non-final configurations
+        :param do_raise: boolean on whether to raise a warning or just fail
 
         :returns: Error dict with reason of validation failure
                   or True
         """
-        # TODO: Raise ConfigurationError with reason
-        # Check if required values are missing for final configuration
+        # TODO: Check if required values are missing for final configuration
         if custom_vals is None:
             custom_vals = {}
 
@@ -466,11 +480,15 @@ def validate_configuration(self, value_ids, custom_vals=None, final=True):
                 common_vals = set(value_ids) & set(line.value_ids.ids)
                 custom_val = custom_vals.get(attr.id)
                 if line.required and not common_vals and not custom_val:
+                    if do_raise:
+                        raise ValidationError(_("No value provided for %s") %
+                                              line.attribute.name)
                     # TODO: Verify custom value type to be correct
                     return False
 
         # Check if all all the values passed are not restricted
-        avail_val_ids = self.values_available(value_ids, value_ids)
+        avail_val_ids = self.values_available(value_ids, value_ids,
+                                              do_raise=do_raise)
         if set(value_ids) - set(avail_val_ids):
             return False
 
@@ -478,7 +496,17 @@ def validate_configuration(self, value_ids, custom_vals=None, final=True):
         custom_attr_ids = self.attribute_line_ids.filtered(
             'custom').mapped('attribute_id').ids
 
-        if not set(custom_vals.keys()) <= set(custom_attr_ids):
+        invalid_custom_vals = set(custom_vals.keys()) - set(custom_attr_ids)
+        if invalid_custom_vals:
+            if do_raise:
+                ProductAttribute = self.env['product.attribute']
+                attributes_names = ', '.join(attr.name
+                                             for attr in
+                                             ProductAttribute.browse(
+                                                 list(invalid_custom_vals)))
+                raise ValidationError(
+                    _('Attributes (%s) cannot hold custom values') %
+                    attributes_names)
             return False
 
         # Check if there are multiple values passed for non-multi attributes
diff --git a/product_configurator/models/product_config.py b/product_configurator/models/product_config.py
index 64ae1a31..0b27f395 100644
--- a/product_configurator/models/product_config.py
+++ b/product_configurator/models/product_config.py
@@ -180,6 +180,11 @@ def onchange_attribute(self):
         string='Restrictions'
     )
 
+    rule_description = fields.Char(
+        string='Rule Description',
+        help='User Displayed error if rule is broken'
+    )
+
     sequence = fields.Integer(string='Sequence', default=10)
 
     _order = 'product_tmpl_id, sequence, id'
@@ -229,7 +234,7 @@ def _check_value_ids(self):
             if not valid:
                 raise ValidationError(
                     _("Values entered for line '%s' generate "
-                      "a incompatible configuration" % cfg_img.name)
+                      "an incompatible configuration" % cfg_img.name)
                 )
 
 
@@ -451,7 +456,7 @@ def write(self, vals):
             for x in self.custom_value_ids
         }
         valid = self.product_tmpl_id.validate_configuration(
-            self.value_ids.ids, custom_val_dict, final=False)
+            self.value_ids.ids, custom_val_dict, final=False, do_raise=True)
         if not valid:
             raise ValidationError(_('Invalid Configuration'))
         return res
diff --git a/product_configurator/tests/test_configuration_rules.py b/product_configurator/tests/test_configuration_rules.py
index 984a3010..649478e6 100644
--- a/product_configurator/tests/test_configuration_rules.py
+++ b/product_configurator/tests/test_configuration_rules.py
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 
 from odoo.tests.common import TransactionCase
+from odoo.exceptions import ValidationError
 
 
 class ConfigurationRules(TransactionCase):
@@ -56,6 +57,10 @@ def test_invalid_configuration(self):
         validation = self.cfg_tmpl.validate_configuration(attr_val_ids)
         self.assertFalse(validation, "Incompatible values (Diesel Fuel -> "
                          "Gasoline Engine) configuration passed validation")
+        self.assertRaises(ValidationError,
+                          self.cfg_tmpl.validate_configuration,
+                          attr_val_ids, do_raise=True,
+                          )
 
     def test_missing_val_configuration(self):
         conf = [
diff --git a/product_configurator/views/product_view.xml b/product_configurator/views/product_view.xml
index 1519dece..69db3c7a 100644
--- a/product_configurator/views/product_view.xml
+++ b/product_configurator/views/product_view.xml
@@ -63,6 +63,7 @@
                                options="{'no_create': True, 'no_create_edit': True}"
                                context="{'show_attribute': False}"/>
                         <field name="domain_id"/>
+                        <field name="rule_description" />
                     </tree>
                 </field>
                 <separator colspan="4" string="Configuration Steps"/>