diff --git a/src/hamster/widgets/activityentry.py b/src/hamster/widgets/activityentry.py
index 15878d6..61a0c7d 100644
--- a/src/hamster/widgets/activityentry.py
+++ b/src/hamster/widgets/activityentry.py
@@ -113,7 +113,7 @@ class ActivityEntry(gtk.Entry):
         for activity in self.external_activities:
             name = activity['name']
             if activity['category']:
-                name = "%s@%s" % name, activity['category']
+                name += "@%s" % activity['category']
             external_names.add(name.lower())
 
         return activity_name, activity_name in external_names
