diff --git a/app/auth/views/register.py b/app/auth/views/register.py
index 6740e579..1799a76f 100644
--- a/app/auth/views/register.py
+++ b/app/auth/views/register.py
@@ -115,7 +115,8 @@ def register():
 
 
 def send_activation_email(user, next_url):
-    # the activation code is valid for 1h
+    # the activation code is valid for 1h and delete all previous codes
+    Session.query(ActivationCode).filter(ActivationCode.user_id == user.id).delete()
     activation = ActivationCode.create(user_id=user.id, code=random_string(30))
     Session.commit()