diff --git a/searx/webapp.py b/searx/webapp.py
index ed8ff1bd..d8289ac0 100644
--- a/searx/webapp.py
+++ b/searx/webapp.py
@@ -64,7 +64,7 @@ from searx.search import Search
 from searx.query import Query
 from searx.autocomplete import searx_bang, backends as autocomplete_backends
 from searx.plugins import plugins
-from searx.preferences import Preferences
+from searx.preferences import Preferences, ValidationException
 
 # check if the pyopenssl, ndg-httpsclient, pyasn1 packages are installed.
 # They are needed for SSL connection without trouble, see #298