diff --git a/models/event.py b/models/event.py
index 0887f02..5e6b77c 100644
--- a/models/event.py
+++ b/models/event.py
@@ -30,8 +30,10 @@ class Event(models.Model):
     @api.depends('date_start', 'date_end')
     def _compute_duration(self):
         for event in self:
-            if event.duration is True:
+            if event.date_start and event.date_end:
                 t1 = fields.Datetime.from_string(event.date_end)
                 t2 = fields.Datetime.from_string(event.date_start)
                 delta = t1 - t2
-                hours = delta.days * 24.0 + round(float(delta.seconds) / 3600.0)
+                event.duration = delta.days * 24.0 + round(float(delta.seconds) / 3600.0)
+            else:
+                event.duration = 0.0