diff --git a/Changelog.md b/Changelog.md
index 3ce71a4..624964a 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -2,7 +2,28 @@
 
 The change log describes what is "Added", "Removed", "Changed" or "Fixed" between each release. 
 
-## UNRELEASED
+## 0.3.0
+
+### Added
+
+- `MessageInterface`
+
+### Changed
+
+- The `Message` is now immutable. Replaced "setters" with "withers".
+- `Storage::create()` and `Storage::update()` has updated signatures to use the`MessageInterface`.
+
+## 0.2.3
+
+### Added
+
+- Support for Symfony 4
+
+## 0.2.2
+
+### Changed
+
+- Documentation change on interface. 
 
 ## 0.2.1
 
diff --git a/src/Model/Message.php b/src/Model/Message.php
index 23ac96b..53e441d 100644
--- a/src/Model/Message.php
+++ b/src/Model/Message.php
@@ -11,12 +11,7 @@
 
 namespace Translation\Common\Model;
 
-/**
- * A object representation of a translation in a specific language.
- *
- * @author Tobias Nyholm <tobias.nyholm@gmail.com>
- */
-final class Message
+final class Message implements MessageInterface
 {
     /**
      * @var string
@@ -60,7 +55,7 @@ final class Message
      * @param string $translation
      * @param array  $meta
      */
-    public function __construct($key = '', $domain = '', $locale = '', $translation = '', array $meta = [])
+    public function __construct($key, $domain = '', $locale = '', $translation = '', array $meta = [])
     {
         $this->key = $key;
         $this->domain = $domain;
@@ -70,7 +65,7 @@ public function __construct($key = '', $domain = '', $locale = '', $translation
     }
 
     /**
-     * @return string
+     * {@inheritdoc}
      */
     public function getDomain()
     {
@@ -78,19 +73,18 @@ public function getDomain()
     }
 
     /**
-     * @param string $domain
-     *
-     * @return Message
+     * {@inheritdoc}
      */
-    public function setDomain($domain)
+    public function withDomain($domain)
     {
-        $this->domain = $domain;
+        $new = clone $this;
+        $new->domain = $domain;
 
-        return $this;
+        return $new;
     }
 
     /**
-     * @return string
+     * {@inheritdoc}
      */
     public function getKey()
     {
@@ -98,19 +92,7 @@ public function getKey()
     }
 
     /**
-     * @param string $key
-     *
-     * @return Message
-     */
-    public function setKey($key)
-    {
-        $this->key = $key;
-
-        return $this;
-    }
-
-    /**
-     * @return string
+     * {@inheritdoc}
      */
     public function getLocale()
     {
@@ -118,19 +100,18 @@ public function getLocale()
     }
 
     /**
-     * @param string $locale
-     *
-     * @return Message
+     * {@inheritdoc}
      */
-    public function setLocale($locale)
+    public function withLocale($locale)
     {
-        $this->locale = $locale;
+        $new = clone $this;
+        $new->locale = $locale;
 
-        return $this;
+        return $new;
     }
 
     /**
-     * @return string
+     * {@inheritdoc}
      */
     public function getTranslation()
     {
@@ -138,19 +119,18 @@ public function getTranslation()
     }
 
     /**
-     * @param string $translation
-     *
-     * @return Message
+     * {@inheritdoc}
      */
-    public function setTranslation($translation)
+    public function withTranslation($translation)
     {
-        $this->translation = $translation;
+        $new = clone $this;
+        $new->translation = $translation;
 
-        return $this;
+        return $new;
     }
 
     /**
-     * @return array
+     * {@inheritdoc}
      */
     public function getAllMeta()
     {
@@ -158,41 +138,36 @@ public function getAllMeta()
     }
 
     /**
-     * @param array $meta
-     *
-     * @return Message
+     * {@inheritdoc}
      */
-    public function setMeta(array $meta)
+    public function withMeta(array $meta)
     {
-        $this->meta = $meta;
+        $new = clone $this;
+        $new->meta = $meta;
 
-        return $this;
+        return $new;
     }
 
     /**
-     * @param string $key
-     * @param string $value
-     *
-     * @return $this
+     * {@inheritdoc}
      */
-    public function addMeta($key, $value)
+    public function withAddedMeta($key, $value)
     {
-        $this->meta[$key] = $value;
+        $new = clone $this;
+        $new->meta[$key] = $value;
 
-        return $this;
+        return $new;
     }
 
     /**
-     * @param string $key
-     *
-     * @return mixed|null
+     * {@inheritdoc}
      */
-    public function getMeta($key)
+    public function getMeta($key, $default = null)
     {
-        if (isset($this->meta[$key])) {
+        if (array_key_exists($key, $this->meta)) {
             return $this->meta[$key];
         }
 
-        return;
+        return $default;
     }
 }
diff --git a/src/Model/MessageInterface.php b/src/Model/MessageInterface.php
new file mode 100644
index 0000000..a80e541
--- /dev/null
+++ b/src/Model/MessageInterface.php
@@ -0,0 +1,109 @@
+<?php
+
+/*
+ * This file is part of the PHP Translation package.
+ *
+ * (c) PHP Translation team <tobias.nyholm@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Translation\Common\Model;
+
+/**
+ * A object representation of a translation in a specific language.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+interface MessageInterface
+{
+    /**
+     * @return string
+     */
+    public function getDomain();
+
+    /**
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * changed request target.
+     *
+     * @param string $domain
+     *
+     * @return static
+     */
+    public function withDomain($domain);
+
+    /**
+     * @return string
+     */
+    public function getKey();
+
+    /**
+     * @return string
+     */
+    public function getLocale();
+
+    /**
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * changed request target.
+     *
+     * @param string $locale
+     *
+     * @return static
+     */
+    public function withLocale($locale);
+
+    /**
+     * @return string
+     */
+    public function getTranslation();
+
+    /**
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * changed request target.
+     *
+     * @param string $translation
+     *
+     * @return static
+     */
+    public function withTranslation($translation);
+
+    /**
+     * @return array
+     */
+    public function getAllMeta();
+
+    /**
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * changed request target.
+     *
+     * @param array $meta
+     *
+     * @return static
+     */
+    public function withMeta(array $meta);
+
+    /**
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * changed request target.
+     *
+     * @param string $key
+     * @param string $value
+     *
+     * @return static
+     */
+    public function withAddedMeta($key, $value);
+
+    /**
+     * @param string     $key
+     * @param mixed|null $default
+     *
+     * @return mixed|null
+     */
+    public function getMeta($key, $default = null);
+}
diff --git a/src/Storage.php b/src/Storage.php
index 412248a..ad60954 100644
--- a/src/Storage.php
+++ b/src/Storage.php
@@ -11,7 +11,7 @@
 
 namespace Translation\Common;
 
-use Translation\Common\Model\Message;
+use Translation\Common\Model\MessageInterface;
 
 /**
  * The storage is a place when you can store your translations. A database, filesystem
@@ -28,7 +28,7 @@ interface Storage
      * @param string $domain
      * @param string $key
      *
-     * @return Message
+     * @return MessageInterface
      */
     public function get($locale, $domain, $key);
 
@@ -36,16 +36,16 @@ public function get($locale, $domain, $key);
      * Create a new translation or asset. If a translation already exist this function
      * will do nothing.
      *
-     * @param Message $message
+     * @param MessageInterface $message
      */
-    public function create(Message $message);
+    public function create(MessageInterface $message);
 
     /**
      * Update a translation. Creates a translation if there is none to update.
      *
-     * @param Message $message
+     * @param MessageInterface $message
      */
-    public function update(Message $message);
+    public function update(MessageInterface $message);
 
     /**
      * Remove a translation from the storage. If the storage implementation makes
diff --git a/tests/Unit/Model/MessageTest.php b/tests/Unit/Model/MessageTest.php
index b430a52..c341adb 100644
--- a/tests/Unit/Model/MessageTest.php
+++ b/tests/Unit/Model/MessageTest.php
@@ -28,13 +28,11 @@ public function testAccessors()
         $this->assertEquals('locale', $message->getLocale());
         $this->assertEquals('translation', $message->getTranslation());
 
-        $message->setKey('key_foo');
-        $this->assertEquals('key_foo', $message->getKey());
-        $message->setDomain('domain_foo');
+        $message = $message->withDomain('domain_foo');
         $this->assertEquals('domain_foo', $message->getDomain());
-        $message->setLocale('locale_foo');
+        $message = $message->withLocale('locale_foo');
         $this->assertEquals('locale_foo', $message->getLocale());
-        $message->setTranslation('trans_foo');
+        $message = $message->withTranslation('trans_foo');
         $this->assertEquals('trans_foo', $message->getTranslation());
     }
 
@@ -45,11 +43,28 @@ public function testMeta()
         $this->assertEquals(['foo' => 'bar'], $message->getAllMeta());
         $this->assertEquals('bar', $message->getMeta('foo'));
 
-        $message->addMeta('key', 'value');
+        $message = $message->withAddedMeta('key', 'value');
         $this->assertEquals('value', $message->getMeta('key'));
 
-        $message->setMeta(['new' => 'values']);
+        $message = $message->withMeta(['new' => 'values']);
         $this->assertNull($message->getMeta('key'));
         $this->assertEquals('values', $message->getMeta('new'));
     }
+
+    public function testImmutability()
+    {
+        $message = new Message('key', 'domain', 'locale', 'translation', ['foo' => 'bar']);
+
+        $message->withDomain('domain_foo');
+        $message->withLocale('locale_foo');
+        $message->withTranslation('trans_foo');
+        $message->withMeta(['new' => 'values']);
+        $message->withAddedMeta('key', 'value');
+
+        $this->assertEquals('key', $message->getKey());
+        $this->assertEquals('domain', $message->getDomain());
+        $this->assertEquals('locale', $message->getLocale());
+        $this->assertEquals('translation', $message->getTranslation());
+        $this->assertEquals(['foo' => 'bar'], $message->getAllMeta());
+    }
 }