diff --git a/backend/geonature/utils/config_schema.py b/backend/geonature/utils/config_schema.py
index 395bc4e347..1e5648df7b 100644
--- a/backend/geonature/utils/config_schema.py
+++ b/backend/geonature/utils/config_schema.py
@@ -4,6 +4,8 @@
 
 import os
 
+from urllib.parse import urlsplit
+
 from marshmallow import (
     Schema,
     fields,
@@ -590,3 +592,13 @@ def insert_module_config(self, data, **kwargs):
                 continue
             data[module_code] = get_module_config(dist)
         return data
+
+    @post_load
+    def infer_application_root(self, data, **kwargs):
+        """
+        Determine APPLICATION_ROOT from URL_APPLICATION
+        The parameter APPLICATION_ROOT is used by Flask tu set the cookie path (use by Flask-Login for Flask Admin)
+        """
+        split_url = urlsplit(data["URL_APPLICATION"])
+        data["APPLICATION_ROOT"] = split_url.path if split_url.path else "/"
+        return data