diff --git a/flask/wrappers.py b/flask/wrappers.py
index fe0c7bcb..c3b16bc6 100644
--- a/flask/wrappers.py
+++ b/flask/wrappers.py
@@ -177,7 +177,7 @@ class Request(RequestBase):
         ctx = _request_ctx_stack.top
         if ctx is not None:
             if ctx.app.config.get('DEBUG', False):
-                raise BadRequest('Failed to decode JSON object: {}'.format(e))
+                raise BadRequest('Failed to decode JSON object: {0}'.format(e))
         raise BadRequest()
 
     def _load_form_data(self):