diff --git a/app/models/subscription.rb b/app/models/subscription.rb
index 220ae28..b9a79e7 100644
--- a/app/models/subscription.rb
+++ b/app/models/subscription.rb
@@ -44,12 +44,14 @@ def self.new_token
   end
 
   def verify!
-    already_verified = verified_at.present?
-    self.verified_at = Time.zone.now
-    self.unsubscribed_at = nil
-    save!
-
-    send_new_subscriber_notification unless already_verified
+    with_lock do
+      already_verified = verified_at.present?
+      self.verified_at = Time.zone.now
+      self.unsubscribed_at = nil
+      save!
+
+      send_new_subscriber_notification unless already_verified
+    end
   end
 
   # Sends verification email.