diff --git a/src/qtism/data/state/Weight.php b/src/qtism/data/state/Weight.php
index <HASH>..<HASH> 100644
--- a/src/qtism/data/state/Weight.php
+++ b/src/qtism/data/state/Weight.php
@@ -14,7 +14,7 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  *
- * Copyright (c) 2013-2014 (original work) Open Assessment Technologies SA (under the project TAO-PRODUCT);
+ * Copyright (c) 2013-2016 (original work) Open Assessment Technologies SA (under the project TAO-PRODUCT);
  *
  * @author Jérôme Bogaerts <jerome@taotesting.com>
  * @license GPLv2
@@ -145,4 +145,9 @@ class Weight extends QtiComponent implements QtiIdentifiable
     {
         return new QtiComponentCollection();
     }
+    
+    public function __clone()
+    {
+        $this->setObservers(new SplObjectStorage());
+    }
 }
Reset observers when cloned.