diff --git a/AqlExpression.php b/AqlExpression.php
new file mode 100644
index 0000000..fefaac1
--- /dev/null
+++ b/AqlExpression.php
@@ -0,0 +1,40 @@
+<?php
+/**
+ * User: evgen-d
+ * Date: 08.10.14
+ * Time: 16:00
+ */
+
+namespace devgroup\arangodb;
+
+use yii\base\Object;
+
+class AqlExpression extends Object
+{
+    /**
+     * @var string the AQL expression represented by this object
+     */
+    public $expression;
+
+
+    /**
+     * Constructor.
+     * @param string $expression the AQL expression represented by this object
+     * @param array $config additional configurations for this object
+     */
+    public function __construct($expression, $config = [])
+    {
+        $this->expression = $expression;
+        parent::__construct($config);
+    }
+
+    /**
+     * The PHP magic function converting an object into a string.
+     * @return string the AQL expression.
+     */
+    public function __toString()
+    {
+        return $this->expression;
+    }
+}
+ 
\ No newline at end of file
diff --git a/Query.php b/Query.php
index ba9f9a3..a8a8a71 100644
--- a/Query.php
+++ b/Query.php
@@ -480,7 +480,7 @@ class Query extends Component implements QueryInterface
 
     public function insert($collection, $columns, $params = [], $db = null)
     {
-        $doc = Json::encode($columns);
+        $doc = Serializer::encode($columns);
 
         $clauses = [
             "INSERT $doc IN {$this->quoteCollectionName($collection)}",
@@ -587,7 +587,7 @@ class Query extends Component implements QueryInterface
     protected function buildUpdate($collection, $columns)
     {
         return 'UPDATE ' . $collection . ' WITH '
-            . (is_array($columns) ? Json::encode($columns) : $columns) . ' IN '
+            . Serializer::encode($columns) . ' IN '
             . $this->quoteCollectionName($collection);
     }
 
diff --git a/Serializer.php b/Serializer.php
new file mode 100644
index 0000000..202e131
--- /dev/null
+++ b/Serializer.php
@@ -0,0 +1,59 @@
+<?php
+/**
+ * User: evgen-d
+ * Date: 08.10.14
+ * Time: 16:04
+ */
+
+namespace devgroup\arangodb;
+
+use yii\base\Arrayable;
+
+class Serializer
+{
+    public static function encode($value, $options = 0)
+    {
+        $expressions = [];
+        $value = static::processData($value, $expressions, uniqid());
+        $json = json_encode($value, $options);
+
+        return empty($expressions) ? $json : strtr($json, $expressions);
+    }
+
+    protected static function processData($data, &$expressions, $expPrefix)
+    {
+        if (is_object($data)) {
+            if ($data instanceof AqlExpression) {
+                $token = "!{[$expPrefix=" . count($expressions) . ']}!';
+                $expressions['"' . $token . '"'] = $data->expression;
+
+                return $token;
+            } elseif ($data instanceof \JsonSerializable) {
+                $data = $data->jsonSerialize();
+            } elseif ($data instanceof Arrayable) {
+                $data = $data->toArray();
+            } else {
+                $result = [];
+                foreach ($data as $name => $value) {
+                    $result[$name] = $value;
+                }
+                $data = $result;
+            }
+
+            if ($data === []) {
+                return new \stdClass();
+            }
+        }
+
+        if (is_array($data)) {
+            foreach ($data as $key => $value) {
+                if (is_array($value) || is_object($value)) {
+                    $data[$key] = static::processData($value, $expressions, $expPrefix);
+                }
+            }
+        }
+
+        return $data;
+    }
+}
+ 
\ No newline at end of file