diff --git a/course/models.py b/course/models.py
index 4aaf5971b..165b452c4 100644
--- a/course/models.py
+++ b/course/models.py
@@ -455,7 +455,7 @@ def clean(self):
         if self.instance_name in RESERVED:
             errors['instance_name'] = format_lazy(_("You cannot use word '{}' as an instance name."), self.instance_name)
         if self.url in RESERVED:
-            errors['url'] = format_lazy(_("You cannot use word '{}' in the url."), self.instance_name)
+            errors['url'] = format_lazy(_("You cannot use word '{}' in the url."), self.url)
         if self.ending_time <= self.starting_time:
             errors['ending_time'] = _("Ending time must be later than starting time.")
         if self.lifesupport_time and self.lifesupport_time < self.ending_time: