diff --git a/colloscope/icalexport.py b/colloscope/icalexport.py
index e89a485..bc7a8b0 100644
--- a/colloscope/icalexport.py
+++ b/colloscope/icalexport.py
@@ -59,7 +59,7 @@ def to_calendar(etudiant, periode):
         event.add("organizer", organizer)
 
         for e in rotation.groupe_effectif():
-            attendee = vCalAddress("mailto:{emailize(e.nom, prenom=e.prenom)}")
+            attendee = vCalAddress(f"mailto:{emailize(e.nom, prenom=e.prenom)}")
             attendee.params["cn"] = vText(str(e))
             attendee.params["role"] = vText("Etudiant")