diff --git a/app.py b/app.py
index 13f51fe..240bd31 100644
--- a/app.py
+++ b/app.py
@@ -549,7 +549,7 @@ def add_user():
     if not user:
         errors['email'] = 'E-Mail Adresse nicht gefunden.'
 
-    if user.id == current_user.id:
+    if user and user.id == current_user.id:
         errors['email'] = 'Du kannst dich nicht selbst hinzufügen.'
 
     # Check if user is already in the habit list