diff --git a/modules/voipcall/voipsession.inc b/modules/voipcall/voipsession.inc
index ec291f7..827c2c5 100644
--- a/modules/voipcall/voipsession.inc
+++ b/modules/voipcall/voipsession.inc
@@ -5,7 +5,7 @@ class VoipSession {
   private $session_data;
 
   function __construct($session_data = NULL) {
-    $this->session_data = $session_data;
+    $this->session_data = $session_data ?? new \stdClass();
   }
 
   /**