Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.977
diff -u -p -r1.977 common.inc
--- includes/common.inc	26 Aug 2009 15:00:17 -0000	1.977
+++ includes/common.inc	27 Aug 2009 05:11:50 -0000
@@ -2576,7 +2576,7 @@ function drupal_get_css($css = NULL) {
     $css = drupal_add_css();
   }
 
-  $preprocess_css = (variable_get('preprocess_css', FALSE) && (!defined('MAINTENANCE_MODE') || MAINTENANCE_MODE != 'update'));
+  $preprocess_css = (variable_get('preprocess_css', 1) && (!defined('MAINTENANCE_MODE') || MAINTENANCE_MODE != 'update'));
   $directory = file_directory_path('public');
   $is_writable = is_dir($directory) && is_writable($directory);
 
Index: modules/block/block.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/block/block.test,v
retrieving revision 1.26
diff -u -p -r1.26 block.test
--- modules/block/block.test	26 Aug 2009 10:53:45 -0000	1.26
+++ modules/block/block.test	27 Aug 2009 05:11:50 -0000
@@ -229,6 +229,7 @@ class NonDefaultBlockAdmin extends Drupa
   function testNonDefaultBlockAdmin() {
     $admin_user = $this->drupalCreateUser(array('administer blocks', 'administer site configuration'));
     $this->drupalLogin($admin_user);
+    variable_set('preprocess_css', 0);
     $this->drupalPost('admin/appearance', array('status[stark]' => 1), t('Save configuration'));
     $this->drupalGet('admin/structure/block/list/stark');
     $this->assertRaw('stark/layout.css', t('Stark CSS found'));
Index: modules/system/system.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.admin.inc,v
retrieving revision 1.197
diff -u -p -r1.197 system.admin.inc
--- modules/system/system.admin.inc	26 Aug 2009 10:53:45 -0000	1.197
+++ modules/system/system.admin.inc	27 Aug 2009 05:11:50 -0000
@@ -1440,7 +1440,7 @@ function system_performance_settings() {
   $form['bandwidth_optimization']['preprocess_css'] = array(
     '#type' => 'checkbox',
     '#title' => t('Aggregate and compress CSS files into one file.'),
-    '#default_value' => intval(variable_get('preprocess_css', 0) && $is_writable),
+    '#default_value' => intval(variable_get('preprocess_css', 1) && $is_writable),
     '#disabled' => $disabled,
   );
   $form['bandwidth_optimization']['preprocess_js'] = array(