diff --git a/webapp/services/BlockChainService.php b/webapp/services/BlockChainService.php
index eb2ca5ee..e09769f7 100644
--- a/webapp/services/BlockChainService.php
+++ b/webapp/services/BlockChainService.php
@@ -135,7 +135,7 @@ class BlockChainService {
                     'params' => $rspObj['params']
                 );
             } else {
-                myself()->_rspErr(500,  'server internal error 4' . $rspObj);
+                myself()->_rspErr(500,  'server internal error 4' . json_encode($rspObj));
                 die();
                 return;
             }