diff --git a/horizon/middleware/operation_log.py b/horizon/middleware/operation_log.py
index 8bcaf84aaf..4119ff5670 100644
--- a/horizon/middleware/operation_log.py
+++ b/horizon/middleware/operation_log.py
@@ -187,4 +187,7 @@ class OperationLogMiddleware(object):
                 [up_file.name for up_file in files])
             params['file_name'] = filenames
 
-        return json.dumps(params, ensure_ascii=False)
+        try:
+            return json.dumps(params, ensure_ascii=False)
+        except Exception:
+            return 'Unserializable Object'