diff --git a/src/MeasurementProtocol.php b/src/MeasurementProtocol.php
index dcbaa4b..6bb1ee0 100644
--- a/src/MeasurementProtocol.php
+++ b/src/MeasurementProtocol.php
@@ -15,7 +15,7 @@ class MeasurementProtocol
 
     public function __construct()
     {
-        $this->clientId = session(config('tagmanager.measurement_protocol_client_id_session_key'));
+        $this->clientId = session(config('tagmanager.measurement_protocol_client_id_session_key'), '');
     }
 
     public function event(string $name, array $params = null): array