diff --git a/src/pyj/read_book/iframe.pyj b/src/pyj/read_book/iframe.pyj
index 40da5f35f9..a6911ea549 100644
--- a/src/pyj/read_book/iframe.pyj
+++ b/src/pyj/read_book/iframe.pyj
@@ -129,7 +129,8 @@ class IframeBoss:
         self.encrypted_communications = True
 
     def onerror(self, msg, script_url, line_number, column_number, error_object):
-        console.log(error_object)
+        if error_object:
+            console.log(error_object)
         try:
             fname = script_url.rpartition('/')[-1] or script_url
             msg = msg + '<br><span style="font-size:smaller">' + 'Error at {}:{}:{}'.format(fname, line_number, column_number or '') + '</span>'