--- mail_headers/mail_headers.install	2012-04-20 16:20:12.000000000 -0500
+++ mail_headers/mail_headers.install.new	2012-04-20 15:54:42.000000000 -0500
@@ -26,6 +26,6 @@
 /**
  * Implements hook_disable().
  */
-function mail_headers_disbale() {
-  variable_del('mail_system');
+function mail_headers_disable() {
+  variable_set('mail_system', array('default-system' => 'DefaultMailSystem'));
 }
\ No newline at end of file