diff --git a/includes/mail.inc b/includes/mail.inc
index bbb5535..07a5055 100644
--- a/includes/mail.inc
+++ b/includes/mail.inc
@@ -10,7 +10,7 @@
  *
  * $conf['mail_line_endings'] will override this setting.
  */
-define('MAIL_LINE_ENDINGS', isset($_SERVER['WINDIR']) || strpos($_SERVER['SERVER_SOFTWARE'], 'Win32') !== FALSE ? "\r\n" : "\n");
+define('MAIL_LINE_ENDINGS', isset($_SERVER['WINDIR']) || (isset($_SERVER['SERVER_SOFTWARE']) && strpos($_SERVER['SERVER_SOFTWARE'], 'Win32') !== FALSE) ? "\r\n" : "\n");
 
 /**
  * Composes and optionally sends an e-mail message.
diff --git a/modules/system/system.install b/modules/system/system.install
index 7b66767..d0aa734 100644
--- a/modules/system/system.install
+++ b/modules/system/system.install
@@ -47,7 +47,7 @@ function system_requirements($phase) {
   }
 
   // Web server information.
-  $software = $_SERVER['SERVER_SOFTWARE'];
+  $software = isset($_SERVER['SERVER_SOFTWARE']) ? $_SERVER['SERVER_SOFTWARE'] : '';
   $requirements['webserver'] = array(
     'title' => $t('Web server'),
     'value' => $software,