diff --git a/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
index e081be5..029a58b 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
@@ -33,14 +33,11 @@ class YamlFileLoader extends FileLoader
     private $yamlParser;
 
     /**
-     * Loads a Yaml file.
-     *
-     * @param mixed  $file The resource
-     * @param string $type The resource type
+     * {@inheritdoc}
      */
-    public function load($file, $type = null)
+    public function load($resource, $type = null)
     {
-        $path = $this->locator->locate($file);
+        $path = $this->locator->locate($resource);
 
         $content = $this->loadFile($path);
 
@@ -52,10 +49,14 @@ class YamlFileLoader extends FileLoader
         }
 
         // imports
-        $this->parseImports($content, $file);
+        $this->parseImports($content, $path);
 
         // parameters
         if (isset($content['parameters'])) {
+            if (!is_array($content['parameters'])) {
+                throw new InvalidArgumentException(sprintf('The "parameters" key should contain an array in %s. Check your YAML syntax.', $resource));
+            }
+
             foreach ($content['parameters'] as $key => $value) {
                 $this->container->setParameter($key, $this->resolveServices($value));
             }
@@ -65,16 +66,11 @@ class YamlFileLoader extends FileLoader
         $this->loadFromExtensions($content);
 
         // services
-        $this->parseDefinitions($content, $file);
+        $this->parseDefinitions($content, $resource);
     }
 
     /**
-     * Returns true if this class supports the given resource.
-     *
-     * @param mixed  $resource A resource
-     * @param string $type     The resource type
-     *
-     * @return Boolean true if this class supports the given resource, false otherwise
+     * {@inheritdoc}
      */
     public function supports($resource, $type = null)
     {
@@ -93,9 +89,17 @@ class YamlFileLoader extends FileLoader
             return;
         }
 
+        if (!is_array($content['imports'])) {
+            throw new InvalidArgumentException(sprintf('The "imports" key should contain an array in %s. Check your YAML syntax.', $file));
+        }
+
         foreach ($content['imports'] as $import) {
+            if (!is_array($import)) {
+                throw new InvalidArgumentException(sprintf('The values in the "imports" key should be arrays in %s. Check your YAML syntax.', $file));
+            }
+
             $this->setCurrentDir(dirname($file));
-            $this->import($import['resource'], null, isset($import['ignore_errors']) ? (Boolean) $import['ignore_errors'] : false, $file);
+            $this->import($import['resource'], null, isset($import['ignore_errors']) ? (bool) $import['ignore_errors'] : false, $file);
         }
     }
 
@@ -111,6 +115,10 @@ class YamlFileLoader extends FileLoader
             return;
         }
 
+        if (!is_array($content['services'])) {
+            throw new InvalidArgumentException(sprintf('The "services" key should contain an array in %s. Check your YAML syntax.', $file));
+        }
+
         foreach ($content['services'] as $id => $service) {
             $this->parseDefinition($id, $service, $file);
         }
@@ -131,8 +139,14 @@ class YamlFileLoader extends FileLoader
             $this->container->setAlias($id, substr($service, 1));
 
             return;
-        } elseif (isset($service['alias'])) {
-            $public = !array_key_exists('public', $service) || (Boolean) $service['public'];
+        }
+
+        if (!is_array($service)) {
+            throw new InvalidArgumentException(sprintf('A service definition must be an array or a string starting with "@" but %s found for service "%s" in %s. Check your YAML syntax.', gettype($service), $id, $file));
+        }
+
+        if (isset($service['alias'])) {
+            $public = !array_key_exists('public', $service) || (bool) $service['public'];
             $this->container->setAlias($id, new Alias($service['alias'], $public));
 
             return;
@@ -205,6 +219,10 @@ class YamlFileLoader extends FileLoader
         }
 
         if (isset($service['calls'])) {
+            if (!is_array($service['calls'])) {
+                throw new InvalidArgumentException(sprintf('Parameter "calls" must be an array for service "%s" in %s. Check your YAML syntax.', $id, $file));
+            }
+
             foreach ($service['calls'] as $call) {
                 $args = isset($call[1]) ? $this->resolveServices($call[1]) : array();
                 $definition->addMethodCall($call[0], $args);
@@ -213,10 +231,14 @@ class YamlFileLoader extends FileLoader
 
         if (isset($service['tags'])) {
             if (!is_array($service['tags'])) {
-                throw new InvalidArgumentException(sprintf('Parameter "tags" must be an array for service "%s" in %s.', $id, $file));
+                throw new InvalidArgumentException(sprintf('Parameter "tags" must be an array for service "%s" in %s. Check your YAML syntax.', $id, $file));
             }
 
             foreach ($service['tags'] as $tag) {
+                if (!is_array($tag)) {
+                    throw new InvalidArgumentException(sprintf('A "tags" entry must be an array for service "%s" in %s. Check your YAML syntax.', $id, $file));
+                }
+
                 if (!isset($tag['name'])) {
                     throw new InvalidArgumentException(sprintf('A "tags" entry is missing a "name" key for service "%s" in %s.', $id, $file));
                 }
@@ -226,7 +248,7 @@ class YamlFileLoader extends FileLoader
 
                 foreach ($tag as $attribute => $value) {
                     if (!is_scalar($value) && null !== $value) {
-                        throw new InvalidArgumentException(sprintf('A "tags" attribute must be of a scalar-type for service "%s", tag "%s", attribute "%s" in %s.', $id, $name, $attribute, $file));
+                        throw new InvalidArgumentException(sprintf('A "tags" attribute must be of a scalar-type for service "%s", tag "%s", attribute "%s" in %s. Check your YAML syntax.', $id, $name, $attribute, $file));
                     }
                 }
 
@@ -234,6 +256,11 @@ class YamlFileLoader extends FileLoader
             }
         }
 
+        if (isset($service['decorates'])) {
+            $renameId = isset($service['decoration_inner_name']) ? $service['decoration_inner_name'] : null;
+            $definition->setDecoratedService($service['decorates'], $renameId);
+        }
+
         $this->container->setDefinition($id, $definition);
     }
 
@@ -243,6 +270,8 @@ class YamlFileLoader extends FileLoader
      * @param string $file
      *
      * @return array The file content
+     *
+     * @throws InvalidArgumentException when the given file is not a local file or when it does not exist
      */
     protected function loadFile($file)
     {
@@ -278,7 +307,7 @@ class YamlFileLoader extends FileLoader
         }
 
         if (!is_array($content)) {
-            throw new InvalidArgumentException(sprintf('The service file "%s" is not valid.', $file));
+            throw new InvalidArgumentException(sprintf('The service file "%s" is not valid. It should contain an array. Check your YAML syntax.', $file));
         }
 
         foreach (array_keys($content) as $namespace) {
@@ -304,9 +333,9 @@ class YamlFileLoader extends FileLoader
     /**
      * Resolves services.
      *
-     * @param string $value
+     * @param string|array $value
      *
-     * @return Reference
+     * @return array|string|Reference
      */
     private function resolveServices($value)
     {