diff --git a/db/migrate/4_add_unique_index_to_friendships.rb b/db/migrate/4_add_unique_index_to_friendships.rb
index 7341340..a04279d 100644
--- a/db/migrate/4_add_unique_index_to_friendships.rb
+++ b/db/migrate/4_add_unique_index_to_friendships.rb
@@ -8,7 +8,9 @@ class AddUniqueIndexToFriendships < ActiveRecord::Migration; end
   disable_ddl_transaction!
 
   def self.up
-    add_index :friendships, [:friendable_id, :friend_id], unique: true, algorithm: :concurrently unless index_exists? (:friendable_id, :friend_id)
+    return if index_exists?(:friendships, [:friendable_id, :friend_id])
+
+    add_index :friendships, [:friendable_id, :friend_id], unique: true, algorithm: :concurrently
   end
 
   def self.down