diff --git a/includes/bootstrap.inc b/includes/bootstrap.inc
index d857f65..67db7dd 100644
--- a/includes/bootstrap.inc
+++ b/includes/bootstrap.inc
@@ -562,7 +562,7 @@ function drupal_get_filename($type, $name, $filename = NULL) {
  */
 function variable_init($conf = array(), $regenerate = FALSE, $recursion_depth = 0) {
   // NOTE: caching the variables improves performance by 20% when serving cached pages.
-  if (!$regenerate && $cached = cache_get('variables', 'cache')) {
+  if ((!$regenerate && $cached = cache_get('variables', 'cache')) && !empty($cached->data)) {
     $variables = $cached->data;
   }
   else {
@@ -571,9 +571,19 @@ function variable_init($conf = array(), $regenerate = FALSE, $recursion_depth =
       while ($variable = db_fetch_object($result)) {
         $variables[$variable->name] = unserialize($variable->value);
       }
-      cache_set('variables', $variables);
-      if (!defined('MAINTENANCE_MODE')) {
-        lock_release('variable_cache_regenerate');
+      if (!empty($variables)) {
+        cache_set('variables', $variables);
+        if (!defined('MAINTENANCE_MODE')) {
+          lock_release('variable_cache_regenerate');
+        }
+      }
+      else {
+        // Prevent this request from harming anything due to default variable values.
+        if (!defined('MAINTENANCE_MODE')) {
+          lock_release('variable_cache_regenerate');
+        }
+        drupal_set_header($_SERVER['SERVER_PROTOCOL'] .' 500 Internal Server Error');
+        exit;
       }
     }
     else {