diff --git a/includes/module.inc b/includes/module.inc
index 28bca23..efc5a0e 100644
--- a/includes/module.inc
+++ b/includes/module.inc
@@ -933,7 +933,7 @@ function drupal_required_modules() {
  *   context needs to be provided to implementations, then this should be an
  *   associative array as described above.
  */
-function drupal_alter($type, &$data, &$context1 = NULL, &$context2 = NULL) {
+function drupal_alter($type, &$data, &$context1 = NULL, &$context2 = NULL, &$context3 = NULL) {
   // Use the advanced drupal_static() pattern, since this is called very often.
   static $drupal_static_fast;
   if (!isset($drupal_static_fast)) {
@@ -1046,6 +1046,6 @@ function drupal_alter($type, &$data, &$context1 = NULL, &$context2 = NULL) {
   }
 
   foreach ($functions[$cid] as $function) {
-    $function($data, $context1, $context2);
+    $function($data, $context1, $context2, $context3);
   }
 }