diff --git a/src/Client.php b/src/Client.php
index 8c7e6a2..4a84519 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -125,7 +125,8 @@ class Client
         try {
             $body = \GuzzleHttp\json_decode($resp->getBody(), true);
             if (isset($body['error']) && isset($body['error']['code']) && isset($body['error']['message'])) {
-                throw new RpcServerException($body['error']['message'], $body['error']['code']);
+                $message = is_array($body['error']['message']) ? json_encode($body['error']['message']) : $body['error']['message'];
+                throw new RpcServerException($message, $body['error']['code']);
             }
             return $body['result'];