diff --git a/app/__init__.py b/app/__init__.py
index 5b37c57bb..3f2d11606 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -36,6 +36,7 @@ from notifications_utils.formatters import formatted_list
 from notifications_utils.sanitise_text import SanitiseASCII
 from werkzeug.exceptions import abort
 from werkzeug.local import LocalProxy
+from werkzeug.routing import RequestRedirect
 
 from app import proxy_fix
 from app.config import configs
@@ -532,6 +533,10 @@ def register_errorhandlers(application):  # noqa (C901 too complex)
             error_code = 500
         return _error_response(error_code)
 
+    @application.errorhandler(400)
+    def handle_400(error):
+        return _error_response(400)
+
     @application.errorhandler(410)
     def handle_gone(error):
         return _error_response(410)
@@ -579,6 +584,10 @@ def register_errorhandlers(application):  # noqa (C901 too complex)
         ), 400)
         return useful_headers_after_request(resp)
 
+    @application.errorhandler(RequestRedirect)
+    def handle_301(error):
+        return error
+
     @application.errorhandler(500)
     @application.errorhandler(Exception)
     def handle_bad_request(error):
diff --git a/requirements.txt b/requirements.txt
index b34aa9329..904383aad 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 ago==0.0.92
-Flask==0.12.2
+Flask==1.0.2
 Flask-WTF==0.14.2
 Flask-Login==0.4.1