diff --git a/addons/web/static/src/js/coresetup.js b/addons/web/static/src/js/coresetup.js
index 7d37dc2261d..1d6acf164d0 100644
--- a/addons/web/static/src/js/coresetup.js
+++ b/addons/web/static/src/js/coresetup.js
@@ -125,7 +125,12 @@ instance.web.Session = instance.web.JsonRPC.extend( /** @lends instance.web.Sess
         for(var i=0; i<cookies.length; ++i) {
             var cookie = cookies[i].replace(/^\s*/, '');
             if(cookie.indexOf(nameEQ) === 0) {
-                return JSON.parse(decodeURIComponent(cookie.substring(nameEQ.length)));
+                try {
+                    return JSON.parse(decodeURIComponent(cookie.substring(nameEQ.length)));
+                } catch (err) {
+                    // wrong cookie, delete it
+                    this.set_cookie(name, '', -1);
+                }
             }
         }
         return null;