diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index 3e4e7d1..80a70f9 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -720,7 +720,7 @@ module ActionMailer #:nodoc:
 
       def perform_delivery_sendmail(mail)
         sendmail_args = sendmail_settings[:arguments]
-        sendmail_args += " -f \"#{mail['return-path']}\"" if mail['return-path']
+        sendmail_args += " -f \"#{mail['return-path'].spec}\"" if mail['return-path']
         IO.popen("#{sendmail_settings[:location]} #{sendmail_args}","w+") do |sm|
           sm.print(mail.encoded.gsub(/\r/, ''))
           sm.flush