--- a/cubicweb/web/views/json.py	Tue Oct 09 16:24:12 2018 +0200
+++ b/cubicweb/web/views/json.py	Mon Oct 29 10:04:31 2018 +0100
@@ -138,8 +138,8 @@
 
     The returned json object will contain err / traceback informations.
     """
-    __select__ = (management.ErrorView.__select__ &
-                  _requested_vid('jsonexport', 'ejsonexport'))
+    __select__ = (management.ErrorView.__select__
+                  & _requested_vid('jsonexport', 'ejsonexport'))
 
     def call(self):
         errmsg, exclass, excinfo = self._excinfo()