diff --git a/src/rc3platform/settings/base.py b/src/rc3platform/settings/base.py
index 95a5b9be55b64aa082335663b66c192362cc0646..8fdfbf9ed1db4e0321f5b81de44ebaf087a456a6 100644
--- a/src/rc3platform/settings/base.py
+++ b/src/rc3platform/settings/base.py
@@ -320,7 +320,7 @@ WORKADVENTURE_BACKEND_PUSH_ON_MAPSERVICE_DATA = True
 # ----------------------------------
 
 # base domain of the frontend (used to generate links in API and BackOffice, not in the plain UI itself)
-PLAINUI_BASE_URL = os.getenv('PLAINUI_BASE_URL', default=None)
+PLAINUI_BASE_URL = os.getenv('PLAINUI_BASE_URL', default='')
 
 # Database ID of the active conference for the PlainUI.
 # To initialize create a conference in the backend, then configure the conference, then restart the UI workers