diff --git a/addons/http_routing/models/ir_http.py b/addons/http_routing/models/ir_http.py
index 628887090af..6621b0a58bc 100644
--- a/addons/http_routing/models/ir_http.py
+++ b/addons/http_routing/models/ir_http.py
@@ -183,7 +183,7 @@ def url_for(url_from, lang_code=None, no_rewrite=False):
 
     # don't try to match route if we know that no rewrite has been loaded.
     routing = getattr(request, 'website_routing', None)  # not modular, but not overridable
-    if not request.env['ir.http']._rewrite_len.get(routing):
+    if not getattr(request.env['ir.http'], '_rewrite_len', {}).get(routing):
         no_rewrite = True
 
     # avoid useless check for 1 char URL '/', '#', ... and absolute URL
diff --git a/odoo/addons/base/models/ir_http.py b/odoo/addons/base/models/ir_http.py
index 70730917ae2..8af7ab9bd3c 100644
--- a/odoo/addons/base/models/ir_http.py
+++ b/odoo/addons/base/models/ir_http.py
@@ -82,9 +82,6 @@ class IrHttp(models.AbstractModel):
     # Routing map
     #------------------------------------------------------
 
-    _routing_map = {}
-    _rewrite_len = {}
-
     @classmethod
     def _get_converters(cls):
         return {'model': ModelConverter, 'models': ModelsConverter, 'int': SignedIntConverter}
@@ -253,6 +250,11 @@ class IrHttp(models.AbstractModel):
 
     @classmethod
     def routing_map(cls, key=None):
+
+        if not hasattr(cls, '_routing_map'):
+            cls._routing_map = {}
+            cls._rewrite_len = {}
+
         if key not in cls._routing_map:
             _logger.info("Generating routing map for key %s" % str(key))
             installed = request.registry._init_modules | set(odoo.conf.server_wide_modules)