diff --git a/lib/API/Endpoints/Mailer.php b/lib/API/Endpoints/Mailer.php
index 709e783f18..e04ef135ae 100644
--- a/lib/API/Endpoints/Mailer.php
+++ b/lib/API/Endpoints/Mailer.php
@@ -24,7 +24,7 @@ class Mailer extends APIEndpoint {
     if($result['response'] === false) {
       $error = sprintf(
         __('The email could not be sent: %s', 'mailpoet'),
-        $result['error']
+        $result['error_message']
       );
       return $this->errorResponse(array(APIError::BAD_REQUEST => $error));
     } else {