diff --git a/addons/http_routing/models/ir_http.py b/addons/http_routing/models/ir_http.py
index 571f47918a0..fd7fde19d75 100644
--- a/addons/http_routing/models/ir_http.py
+++ b/addons/http_routing/models/ir_http.py
@@ -427,8 +427,12 @@ class IrHttp(models.AbstractModel):
             request.is_frontend = func.routing.get('website', False)
         except werkzeug.exceptions.NotFound as e:
             # either we have a language prefixed route, either a real 404
-            # in all cases, website processes them
-            request.is_frontend = True
+            # in all cases, website processes them exept if second element is static
+            # Checking static will avoid to generate an expensive 404 web page since
+            # most of the time the browser is loading and inexisting assets or image. A standard 404 is enough.
+            # Earlier check would be difficult since we don't want to break data modules
+            path_components = request.httprequest.path.split('/')
+            request.is_frontend = len(path_components) < 3 or path_components[2] != 'static' or not '.' in path_components[-1]
             routing_error = e
 
         request.is_frontend_multilang = not func or (func and request.is_frontend and func.routing.get('multilang', func.routing['type'] == 'http'))
diff --git a/addons/web/static/tests/chrome/action_manager_tests.js b/addons/web/static/tests/chrome/action_manager_tests.js
index af214a26203..226c8fb2b15 100644
--- a/addons/web/static/tests/chrome/action_manager_tests.js
+++ b/addons/web/static/tests/chrome/action_manager_tests.js
@@ -2190,7 +2190,8 @@ QUnit.module('ActionManager', {
             start: function () {
                 var self = this;
                 return this._super.apply(this, arguments).then(function () {
-                    self.iframe.src = 'test ' + self.iframe.getAttribute('src');
+                    self._rpc({route: self.iframe.getAttribute('src')});
+                    self.iframe.setAttribute('src', 'about:blank');
                 });
             }
         });
@@ -2212,7 +2213,7 @@ QUnit.module('ActionManager', {
                 if (route === '/report/check_wkhtmltopdf') {
                     return Promise.resolve('broken');
                 }
-                if (route === 'test /report/html/some_report') {
+                if (route === '/report/html/some_report') {
                     return Promise.resolve();
                 }
                 return this._super.apply(this, arguments);
@@ -2233,7 +2234,7 @@ QUnit.module('ActionManager', {
             '/web/action/load',
             '/report/check_wkhtmltopdf',
             'warning',
-            'test /report/html/some_report', // report client action's iframe
+            '/report/html/some_report', // report client action's iframe
         ]);
 
         actionManager.destroy();
diff --git a/addons/website/models/ir_http.py b/addons/website/models/ir_http.py
index ef9a9433ce7..de6d88cbbba 100644
--- a/addons/website/models/ir_http.py
+++ b/addons/website/models/ir_http.py
@@ -253,7 +253,8 @@ class Http(models.AbstractModel):
         parent = super(Http, cls)._serve_fallback(exception)
         if parent:  # attachment
             return parent
-
+        if not request.is_frontend:
+            return False
         website_page = cls._serve_page()
         if website_page:
             return website_page