diff --git a/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php b/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php
index 01f0266c45..ed85efa4e0 100644
--- a/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php
+++ b/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php
@@ -1212,7 +1212,7 @@ EOF;
 
             return $this->getServiceCall((string) $value, $value);
         } elseif ($value instanceof Expression) {
-            return $this->getExpressionLanguage()->compile((string) $value, array('container'));
+            return $this->getExpressionLanguage()->compile((string) $value, array('this' => 'container'));
         } elseif ($value instanceof Parameter) {
             return $this->dumpParameter($value);
         } elseif (true === $interpolate && is_string($value)) {
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/containers/container9.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/containers/container9.php
index 19882c0211..582c631fa7 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/containers/container9.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/containers/container9.php
@@ -52,7 +52,7 @@ $container->
     addMethodCall('setBar', array(new Reference('foo2', ContainerInterface::NULL_ON_INVALID_REFERENCE)))->
     addMethodCall('setBar', array(new Reference('foo3', ContainerInterface::IGNORE_ON_INVALID_REFERENCE)))->
     addMethodCall('setBar', array(new Reference('foobaz', ContainerInterface::IGNORE_ON_INVALID_REFERENCE)))->
-    addMethodCall('setBar', array(new Expression('service("foo").foo() ~ parameter("foo")')))
+    addMethodCall('setBar', array(new Expression('service("foo").foo() ~ (container.hasparameter("foo") ? parameter("foo") : "default")')))
 ;
 $container->
     register('factory_service', 'Bar')->
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services9.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services9.php
index 84036928bf..b225259ff6 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services9.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services9.php
@@ -197,7 +197,7 @@ class ProjectServiceContainer extends Container
         if ($this->has('foobaz')) {
             $instance->setBar($this->get('foobaz', ContainerInterface::NULL_ON_INVALID_REFERENCE));
         }
-        $instance->setBar(($this->get("foo")->foo() . $this->getParameter("foo")));
+        $instance->setBar(($this->get("foo")->foo() . (($this->hasparameter("foo")) ? ($this->getParameter("foo")) : ("default"))));
 
         return $instance;
     }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services9_compiled.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services9_compiled.php
index 0dd611e90c..1bb87851fc 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services9_compiled.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services9_compiled.php
@@ -202,7 +202,7 @@ class ProjectServiceContainer extends Container
 
         $instance->setBar($this->get('foo'));
         $instance->setBar(NULL);
-        $instance->setBar(($this->get("foo")->foo() . $this->getParameter("foo")));
+        $instance->setBar(($this->get("foo")->foo() . (($this->hasparameter("foo")) ? ($this->getParameter("foo")) : ("default"))));
 
         return $instance;
     }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/services6.xml b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/services6.xml
index ffc038234f..eb47fe71a1 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/services6.xml
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/services6.xml
@@ -33,7 +33,7 @@
     <service id="method_call1" class="FooClass">
       <call method="setBar" />
       <call method="setBar">
-        <argument type="expression">service("foo").foo() ~ parameter("foo")</argument>
+        <argument type="expression">service("foo").foo() ~ (container.hasparameter("foo") ? parameter("foo") : "default")</argument>
       </call>
     </service>
     <service id="method_call2" class="FooClass">
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/services9.xml b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/services9.xml
index 294ad5c589..95b6e7d686 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/services9.xml
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/services9.xml
@@ -54,7 +54,7 @@
         <argument type="service" id="foobaz" on-invalid="ignore"/>
       </call>
       <call method="setBar">
-        <argument type="expression">service("foo").foo() ~ parameter("foo")</argument>
+        <argument type="expression">service("foo").foo() ~ (container.hasparameter("foo") ? parameter("foo") : "default")</argument>
       </call>
     </service>
     <service id="factory_service" class="Bar" factory-method="getInstance" factory-service="foo.baz"/>
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services6.yml b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services6.yml
index d3c793f2e3..38fdef814c 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services6.yml
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services6.yml
@@ -15,7 +15,7 @@ services:
         calls:
             - [ setBar, [] ]
             - [ setBar ]
-            - [ setBar, ['@=service("foo").foo() ~ parameter("foo")'] ]
+            - [ setBar, ['@=service("foo").foo() ~ (container.hasparameter("foo") ? parameter("foo") : "default")'] ]
     method_call2:
         class: FooClass
         calls:
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services9.yml b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services9.yml
index 6de64ee463..6529192cd6 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services9.yml
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services9.yml
@@ -38,7 +38,7 @@ services:
             - [setBar, ['@?foo2']]
             - [setBar, ['@?foo3']]
             - [setBar, ['@?foobaz']]
-            - [setBar, ['@=service("foo").foo() ~ parameter("foo")']]
+            - [setBar, ['@=service("foo").foo() ~ (container.hasparameter("foo") ? parameter("foo") : "default")']]
 
     factory_service:
         class: Bar
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Loader/XmlFileLoaderTest.php b/src/Symfony/Component/DependencyInjection/Tests/Loader/XmlFileLoaderTest.php
index 95ad9aa742..986e0aa0d1 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Loader/XmlFileLoaderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Loader/XmlFileLoaderTest.php
@@ -210,7 +210,7 @@ class XmlFileLoaderTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals('sc_configure', $services['configurator1']->getConfigurator(), '->load() parses the configurator tag');
         $this->assertEquals(array(new Reference('baz', ContainerInterface::EXCEPTION_ON_INVALID_REFERENCE, false), 'configure'), $services['configurator2']->getConfigurator(), '->load() parses the configurator tag');
         $this->assertEquals(array('BazClass', 'configureStatic'), $services['configurator3']->getConfigurator(), '->load() parses the configurator tag');
-        $this->assertEquals(array(array('setBar', array()), array('setBar', array(new Expression('service("foo").foo() ~ parameter("foo")')))), $services['method_call1']->getMethodCalls(), '->load() parses the method_call tag');
+        $this->assertEquals(array(array('setBar', array()), array('setBar', array(new Expression('service("foo").foo() ~ (container.hasparameter("foo") ? parameter("foo") : "default")')))), $services['method_call1']->getMethodCalls(), '->load() parses the method_call tag');
         $this->assertEquals(array(array('setBar', array('foo', new Reference('foo'), array(true, false)))), $services['method_call2']->getMethodCalls(), '->load() parses the method_call tag');
         $this->assertNull($services['factory_service']->getClass());
         $this->assertEquals('getInstance', $services['factory_service']->getFactoryMethod());
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php b/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
index 83a7ea4f66..1958d11e86 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
@@ -138,7 +138,7 @@ class YamlFileLoaderTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals('sc_configure', $services['configurator1']->getConfigurator(), '->load() parses the configurator tag');
         $this->assertEquals(array(new Reference('baz'), 'configure'), $services['configurator2']->getConfigurator(), '->load() parses the configurator tag');
         $this->assertEquals(array('BazClass', 'configureStatic'), $services['configurator3']->getConfigurator(), '->load() parses the configurator tag');
-        $this->assertEquals(array(array('setBar', array()), array('setBar', array()), array('setBar', array(new Expression('service("foo").foo() ~ parameter("foo")')))), $services['method_call1']->getMethodCalls(), '->load() parses the method_call tag');
+        $this->assertEquals(array(array('setBar', array()), array('setBar', array()), array('setBar', array(new Expression('service("foo").foo() ~ (container.hasparameter("foo") ? parameter("foo") : "default")')))), $services['method_call1']->getMethodCalls(), '->load() parses the method_call tag');
         $this->assertEquals(array(array('setBar', array('foo', new Reference('foo'), array(true, false)))), $services['method_call2']->getMethodCalls(), '->load() parses the method_call tag');
         $this->assertEquals('baz_factory', $services['factory_service']->getFactoryService());
 
diff --git a/src/Symfony/Component/ExpressionLanguage/Parser.php b/src/Symfony/Component/ExpressionLanguage/Parser.php
index db4b5858b1..1c385aceec 100644
--- a/src/Symfony/Component/ExpressionLanguage/Parser.php
+++ b/src/Symfony/Component/ExpressionLanguage/Parser.php
@@ -75,6 +75,16 @@ class Parser
     /**
      * Converts a token stream to a node tree.
      *
+     * The valid names is an array where the values
+     * are the names that the user can use in an expression.
+     *
+     * If the variable name in the compiled PHP code must be
+     * different, define it as the key.
+     *
+     * For instance, ['this' => 'container'] means that the
+     * variable 'container' can be used in the expression
+     * but the compiled code will use 'this'.
+     *
      * @param TokenStream $stream A token stream instance
      * @param array       $names  An array of valid names
      *
@@ -194,7 +204,13 @@ class Parser
                                 throw new SyntaxError(sprintf('Variable "%s" is not valid', $token->value), $token->cursor);
                             }
 
-                            $node = new Node\NameNode($token->value);
+                            // is the name used in the compiled code different
+                            // from the name used in the expression?
+                            if (is_int($name = array_search($token->value, $this->names))) {
+                                $name = $token->value;
+                            }
+
+                            $node = new Node\NameNode($name);
                         }
                 }
                 break;
diff --git a/src/Symfony/Component/ExpressionLanguage/Tests/ParserTest.php b/src/Symfony/Component/ExpressionLanguage/Tests/ParserTest.php
index 4cbab6591f..58229857fc 100644
--- a/src/Symfony/Component/ExpressionLanguage/Tests/ParserTest.php
+++ b/src/Symfony/Component/ExpressionLanguage/Tests/ParserTest.php
@@ -148,6 +148,12 @@ class ParserTest extends \PHPUnit_Framework_TestCase
                 'foo.bar().foo().baz[3]',
                 array('foo'),
             ),
+
+            array(
+                new Node\NameNode('foo'),
+                'bar',
+                array('foo' => 'bar'),
+            ),
         );
     }