diff --git a/imio_teleservices_templatetags/templatetags/imio_teleservices.py b/imio_teleservices_templatetags/templatetags/imio_teleservices.py
index 4638488..1f58445 100644
--- a/imio_teleservices_templatetags/templatetags/imio_teleservices.py
+++ b/imio_teleservices_templatetags/templatetags/imio_teleservices.py
@@ -424,7 +424,8 @@ def format_text(modele, *args):
     len_args = len(args)
     for i in range(0, len_args, 2):
         expression = '{{' + args[i] + '}}'
-        modele = modele.replace(expression, args[i + 1])
+        if args[i + 1] is not None:
+            modele = modele.replace(expression, unlazy(args[i + 1]))
     return modele