Index: includes/file.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/file.inc,v
retrieving revision 1.167
diff -u -p -r1.167 file.inc
--- includes/file.inc	22 Apr 2009 09:45:02 -0000	1.167
+++ includes/file.inc	16 May 2009 23:02:24 -0000
@@ -1798,7 +1798,7 @@ function file_get_mimetype($filename, $m
       'cdr' => 'image/x-coreldraw',
       'pat' => 'image/x-coreldrawpattern',
       'cdt' => 'image/x-coreldrawtemplate',
-      'ico' => 'image/x-icon',
+      'ico' => 'image/vnd.microsoft.icon',
       'art' => 'image/x-jg',
       'jng' => 'image/x-jng',
       'bmp' => 'image/x-ms-bmp',
Index: includes/theme.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/theme.inc,v
retrieving revision 1.485
diff -u -p -r1.485 theme.inc
--- includes/theme.inc	14 May 2009 08:23:14 -0000	1.485
+++ includes/theme.inc	16 May 2009 23:02:24 -0000
@@ -1769,7 +1769,12 @@ function template_preprocess_page(&$vari
 
   // Add favicon.
   if (theme_get_setting('toggle_favicon')) {
-    drupal_add_html_head('<link rel="shortcut icon" href="' . check_url(theme_get_setting('favicon')) . '" type="image/x-icon" />');
+    $favicon = theme_get_setting('favicon');
+    $favicon_type = file_get_mimetype($favicon);
+    if ($favicon_type == 'application/octet-stream') {
+      $favicon_type = 'image/x-icon';
+    }
+    drupal_add_html_head('<link rel="shortcut icon" href="' . check_url($favicon) . '" type="' . $favicon_type . '" />');
   }
 
   // Set up layout variable.