diff --git a/booking.stripe.inc b/booking.stripe.inc
index adb7d93..2cd80e0 100644
--- a/booking.stripe.inc
+++ b/booking.stripe.inc
@@ -237,8 +237,9 @@ function booking_stripe_validate_form_payment($form, &$form_state) {
   }
   catch (\Stripe\Exception\CardException $e) {
     $e_json = $e->getJsonBody();
+    $error = $e_json['error'];
     watchdog('booking', "Detected exception processing Stripe payment : !message . !error", 
-      array('!message' => $e->getMessage(), '!error' => $e_json['error']));
+      array('!message' => $e->getMessage(), '!error' => $error));
     drupal_set_message($e->getMessage(), 'error');    
   }
 }