diff --git a/reference/constraints/Expression.rst b/reference/constraints/Expression.rst
index d491adea2db..b6723ffc371 100644
--- a/reference/constraints/Expression.rst
+++ b/reference/constraints/Expression.rst
@@ -74,7 +74,7 @@ One way to accomplish this is with the Expression constraint:
 
         // src/Acme/DemoBundle/Model/BlogPost.php
         namespace Acme\DemoBundle\Model\BlogPost;
-        
+
         use Symfony\Component\Validator\Constraints as Assert;
 
         /**
@@ -91,23 +91,27 @@ One way to accomplish this is with the Expression constraint:
     .. code-block:: xml
 
         <!-- src/Acme/DemoBundle/Resources/config/validation.xml -->
-        <class name="Acme\DemoBundle\Model\BlogPost">
-            <constraint name="Expression">
-                <option name="expression">
-                    this.getCategory() in ['php', 'symfony'] or !this.isTechnicalPost()
-                </option>
-                <option name="message">
-                    If this is a tech post, the category should be either php or symfony!
-                </option>
-            </constraint>
-        </class>
-
+        <?xml version="1.0" encoding="UTF-8" ?>
+        <constraint-mapping xmlns="http://symfony.com/schema/dic/constraint-mapping"
+            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+            xsi:schemaLocation="http://symfony.com/schema/dic/constraint-mapping http://symfony.com/schema/dic/constraint-mapping/constraint-mapping-1.0.xsd">
+            <class name="Acme\DemoBundle\Model\BlogPost">
+                <constraint name="Expression">
+                    <option name="expression">
+                        this.getCategory() in ['php', 'symfony'] or !this.isTechnicalPost()
+                    </option>
+                    <option name="message">
+                        If this is a tech post, the category should be either php or symfony!
+                    </option>
+                </constraint>
+            </class>
+        </constraint-mapping>
 
     .. code-block:: php
 
         // src/Acme/DemoBundle/Model/BlogPost.php
-        namespace Acme\DemoBundle\Model\BlogPost;
-        
+        namespace Acme\DemoBundle\Model;
+
         use Symfony\Component\Validator\Mapping\ClassMetadata;
         use Symfony\Component\Validator\Constraints as Assert;
 
@@ -129,6 +133,90 @@ expression that must return true in order for validation to pass. To learn
 more about the expression language syntax, see
 :doc:`/components/expression_language/syntax`.
 
+.. sidebar:: Mapping the Error to a Specific Field
+
+    You can also attach the constraint to a specific property and still validate
+    based on the values of the entire entity. This is handy if you want to attach
+    the error to a specific field. In this context, ``value`` represents the value
+    of ``isTechnicalPost``.
+
+    .. configuration-block::
+
+        .. code-block:: yaml
+
+            # src/Acme/DemoBundle/Resources/config/validation.yml
+            Acme\DemoBundle\Model\BlogPost:
+                properties:
+                    isTechnicalPost:
+                        - Expression:
+                            expression: "this.getCategory() in ['php', 'symfony'] or value == false"
+                            message: "If this is a tech post, the category should be either php or symfony!"
+
+        .. code-block:: php-annotations
+
+            // src/Acme/DemoBundle/Model/BlogPost.php
+            namespace Acme\DemoBundle\Model;
+
+            use Symfony\Component\Validator\Constraints as Assert;
+
+            class BlogPost
+            {
+                // ...
+
+                /**
+                 * @Assert\Expression(
+                 *     "this.getCategory() in ['php', 'symfony'] or value == false",
+                 *     message="If this is a tech post, the category should be either php or symfony!"
+                 * )
+                 */
+                private $isTechnicalPost;
+
+                // ...
+            }
+
+        .. code-block:: xml
+
+            <!-- src/Acme/DemoBundle/Resources/config/validation.xml -->
+            <?xml version="1.0" encoding="UTF-8" ?>
+            <constraint-mapping xmlns="http://symfony.com/schema/dic/constraint-mapping"
+                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+                xsi:schemaLocation="http://symfony.com/schema/dic/constraint-mapping http://symfony.com/schema/dic/constraint-mapping/constraint-mapping-1.0.xsd">
+
+                <class name="Acme\DemoBundle\Model\BlogPost">
+                    <property name="isTechnicalPost">
+                        <constraint name="Expression">
+                            <option name="expression">
+                                this.getCategory() in ['php', 'symfony'] or value == false
+                            </option>
+                            <option name="message">
+                                If this is a tech post, the category should be either php or symfony!
+                            </option>
+                        </constraint>
+                    </property>
+                </class>
+            </constraint-mapping>
+
+        .. code-block:: php
+
+            // src/Acme/DemoBundle/Model/BlogPost.php
+            namespace Acme\DemoBundle\Model;
+
+            use Symfony\Component\Validator\Constraints as Assert;
+            use Symfony\Component\Validator\Mapping\ClassMetadata;
+
+            class BlogPost
+            {
+                public static function loadValidatorMetadata(ClassMetadata $metadata)
+                {
+                    $metadata->addPropertyConstraint('isTechnicalPost', new Assert\Expression(array(
+                        'expression' => 'this.getCategory() in ["php", "symfony"] or value == false',
+                        'message' => 'If this is a tech post, the category should be either php or symfony!',
+                    )));
+                }
+
+                // ...
+            }
+
 For more information about the expression and what variables are available
 to you, see the :ref:`expression <reference-constraint-expression-option>`
 option details below.