diff --git a/lib/validates_email_format_of.rb b/lib/validates_email_format_of.rb
index f742e32..8f8a7b4 100644
--- a/lib/validates_email_format_of.rb
+++ b/lib/validates_email_format_of.rb
@@ -299,7 +299,7 @@ def self.deprecation_warn(msg)
     if defined?(ActiveSupport::Deprecation)
       ActiveSupport::Deprecation.warn(msg)
     else
-      warn
+      warn(msg)
     end
   end
 end