diff --git a/core/includes/config.inc b/core/includes/config.inc
index b438977..cb81acc 100644
--- a/core/includes/config.inc
+++ b/core/includes/config.inc
@@ -17,8 +17,8 @@ function config_get_config_directory() {
   global $config_directory_name;
 
   if ($test_prefix = drupal_valid_test_ua()) {
-    $path = conf_path() . '/files/simpletest/config_' . $test_prefix;
-    file_prepare_directory($path, FILE_CREATE_DIRECTORY);
+    // @see DrupalWebTestCase::setUp()
+    $path = conf_path() . '/files/simpletest/' . substr($test_prefix, 10) . '/config';
   }
   else {
     $path = conf_path() . '/files/' . $config_directory_name;
diff --git a/core/modules/simpletest/drupal_web_test_case.php b/core/modules/simpletest/drupal_web_test_case.php
index 5d868a2..591e8a1 100644
--- a/core/modules/simpletest/drupal_web_test_case.php
+++ b/core/modules/simpletest/drupal_web_test_case.php
@@ -1354,7 +1354,8 @@ class DrupalWebTestCase extends DrupalTestCase {
     // Create and set a new configuration directory and signature key.
     // The child site automatically adjusts the global $config_directory_name to
     // a test-prefix-specific directory within the public files directory.
-    $GLOBALS['config_directory_name'] = 'simpletest/config_' . $this->databasePrefix;
+    // @see config_get_config_directory()
+    $GLOBALS['config_directory_name'] = 'simpletest/' . substr($this->databasePrefix, 10) . '/config';
     $this->configFileDirectory = $this->originalFileDirectory . '/' . $GLOBALS['config_directory_name'];
     file_prepare_directory($this->configFileDirectory, FILE_CREATE_DIRECTORY | FILE_MODIFY_PERMISSIONS);
     $GLOBALS['config_signature_key'] = drupal_hash_base64(drupal_random_bytes(55));
@@ -1547,9 +1548,6 @@ class DrupalWebTestCase extends DrupalTestCase {
     // Delete temporary files directory.
     file_unmanaged_delete_recursive($this->originalFileDirectory . '/simpletest/' . substr($this->databasePrefix, 10));
 
-    // Delete temporary config files directory.
-    file_unmanaged_delete_recursive($this->originalFileDirectory . '/simpletest/config_simpletest' . substr($this->databasePrefix, 10));
-
     // Remove all prefixed tables (all the tables in the schema).
     $schema = drupal_get_schema(NULL, TRUE);
     foreach ($schema as $name => $table) {