--- boost.api.inc (saved version)
+++ (current document)
@@ -23,7 +23,7 @@
   $path = drupal_get_normal_path($path); // normalize path
 
   // Never cache the basic user login/registration pages or any administration pages
-  if ($path == 'user' || preg_match('!^user/(login|register|password)!', $path) || preg_match('!^admin!', $path))
+  if ($path == 'user' || preg_match('!^user/(login|register|password)!', $path) || preg_match('!^admin!', $path) || $path == 'logout')
     return FALSE;
 
   // At present, RSS feeds are not cacheable due to content type restrictions