Index: modules/system/system.install
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.install,v
retrieving revision 1.449
diff -u -p -r1.449 system.install
--- modules/system/system.install	26 Feb 2010 06:39:13 -0000	1.449
+++ modules/system/system.install	28 Feb 2010 18:33:09 -0000
@@ -1611,7 +1611,7 @@ function system_update_6051() {
 
   if (!db_column_exists('users', 'signature_format')) {
 
-    // Set future text formats to FILTER_FORMAT_DEFAULT to ensure a safe default
+    // Set future text formats to the fallback format to ensure a safe default
     // when incompatible modules insert into the users table. An actual format
     // will be assigned when users save their signature.
 
@@ -1619,13 +1619,15 @@ function system_update_6051() {
       'type' => 'int',
       'size' => 'small',
       'not null' => TRUE,
-      'default' => FILTER_FORMAT_DEFAULT,
+      'default' => filter_fallback_format(),
       'description' => 'The {filter_formats}.format of the signature.',
     );
 
     db_add_field($ret, 'users', 'signature_format', $schema);
 
     // Set the format of existing signatures to the current default text format.
+    // Although the 'filter_default_format' variable is deprecated, Drupal 7
+    // preserves it in the database for this purpose only.
     if ($current_default_filter = variable_get('filter_default_format', 0)) {
       db_update('users')
         ->fields(array(