diff --git a/lib/prosopite.rb b/lib/prosopite.rb
index 5dee267..f097e3c 100644
--- a/lib/prosopite.rb
+++ b/lib/prosopite.rb
@@ -214,7 +214,7 @@ def send_notifications
       @prosopite_logger ||= false
       @raise ||= false
 
-      notifications_str = ''
+      notifications_str = String.new('')
 
       tc[:prosopite_notifications].each do |queries, kaller|
         notifications_str << "N+1 queries detected:\n"