diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index 6dca80b..683fec3 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -451,15 +451,13 @@ function system_theme_settings($form, &$form_state, $key = '') {
     $form['logo'] = array(
       '#type' => 'fieldset',
       '#title' => t('Logo image settings'),
-      '#description' => t('If toggled on, the following logo will be displayed.'),
       '#attributes' => array('class' => array('theme-settings-bottom')),
     );
     $form['logo']['default_logo'] = array(
       '#type' => 'checkbox',
-      '#title' => t('Use the default logo'),
+      '#title' => t('Use the default logo supplied by the theme'),
       '#default_value' => theme_get_setting('default_logo', $key),
       '#tree' => FALSE,
-      '#description' => t('Check here if you want the theme to use the logo supplied with it.')
     );
     $form['logo']['settings'] = array(
       '#type' => 'container',
@@ -473,14 +471,29 @@ function system_theme_settings($form, &$form_state, $key = '') {
     $logo_path = theme_get_setting('logo_path', $key);
     // If $logo_path is a public:// URI, display the path relative to the files
     // directory; stream wrappers are not end-user friendly.
+    $friendly_logo_path = $logo_path;
     if (file_uri_scheme($logo_path) == 'public') {
-      $logo_path = file_uri_target($logo_path);
+      $friendly_logo_path = file_uri_target($logo_path);
+    }
+    // Prepare local file path for description.
+    if ($logo_path) {
+      $local_file = '/' . strtr($logo_path, array('public:/' => variable_get('file_public_path', conf_path() . '/files')));
+    }
+    elseif ($key) {
+      $local_file = base_path() . drupal_get_path('theme', $key) . '/logo.png';
+    }
+    else {
+      $local_file = base_path() . path_to_theme() . '/logo.png';
     }
     $form['logo']['settings']['logo_path'] = array(
       '#type' => 'textfield',
       '#title' => t('Path to custom logo'),
-      '#default_value' => $logo_path,
-      '#description' => t('The path to the file you would like to use as your logo file instead of the default logo.'),
+      '#default_value' => $friendly_logo_path,
+      '#description' => t('Use <code>@implicit-public-file</code> to reference a file in the public filesystem, <code>@explicit-file</code> for a specific filesystem, or <code>@local-file</code> for an arbitrary local file within this site.', array(
+        '@implicit-public-file' => $friendly_logo_path ? $friendly_logo_path : 'example.png',
+        '@explicit-file' => $logo_path ? $logo_path : 'public://example.png',
+        '@local-file' => $local_file,
+      )),
     );
     $form['logo']['settings']['logo_upload'] = array(
       '#type' => 'file',
@@ -498,9 +511,8 @@ function system_theme_settings($form, &$form_state, $key = '') {
     );
     $form['favicon']['default_favicon'] = array(
       '#type' => 'checkbox',
-      '#title' => t('Use the default shortcut icon.'),
+      '#title' => t('Use the default shortcut icon supplied by the theme'),
       '#default_value' => theme_get_setting('default_favicon', $key),
-      '#description' => t('Check here if you want the theme to use the default shortcut icon.')
     );
     $form['favicon']['settings'] = array(
       '#type' => 'container',
@@ -657,21 +669,36 @@ function system_theme_settings_validate($form, &$form_state) {
  *   the path could not be validated.
  */
 function _system_theme_settings_validate_path($path) {
-  if (drupal_realpath($path)) {
-    // The path is relative to the Drupal root, or is a valid URI.
-    return $path;
+  // Check whether the path is semi-absolute; i.e., pointing to a file in the
+  // document root.
+  if ($path[0] === '/') {
+    if (file_exists(DRUPAL_ROOT . '/' . substr($path, 1))) {
+      return $path;
+    }
+    return FALSE;
   }
-  $uri = 'public://' . $path;
-  if (file_exists($uri)) {
-    return $uri;
+  // Otherwise, it must be a stream wrapper URI.
+  else {
+    // Prepend 'public://' for relative file paths within public filesystem.
+    if (file_uri_scheme($path) === FALSE) {
+      $path = 'public://' . $path;
+    }
+    if (file_exists($path)) {
+      return $path;
+    }
+    return FALSE;
   }
-  return FALSE;
 }
 
 /**
  * Process system_theme_settings form submissions.
  */
 function system_theme_settings_submit($form, &$form_state) {
+  // Exclude unnecessary elements before saving.
+  form_state_values_clean($form_state);
+  $key = $form_state['values']['var'];
+  unset($form_state['values']['var']);
+
   $values = $form_state['values'];
 
   // If the user uploaded a new logo or favicon, save it to a permanent location
@@ -703,10 +730,7 @@ function system_theme_settings_submit($form, &$form_state) {
   if (empty($values['default_favicon']) && !empty($values['favicon_path'])) {
     $values['favicon_mimetype'] = file_get_mimetype($values['favicon_path']);
   }
-  $key = $values['var'];
 
-  // Exclude unnecessary elements before saving.
-  unset($values['var'], $values['submit'], $values['reset'], $values['form_id'], $values['op'], $values['form_build_id'], $values['form_token']);
   variable_set($key, $values);
   drupal_set_message(t('The configuration options have been saved.'));
 
diff --git a/core/modules/system/system.test b/core/modules/system/system.test
index 12797ed..8353e15 100644
--- a/core/modules/system/system.test
+++ b/core/modules/system/system.test
@@ -1600,6 +1600,8 @@ class SystemMainContentFallback extends DrupalWebTestCase {
  * Tests for the theme interface functionality.
  */
 class SystemThemeFunctionalTest extends DrupalWebTestCase {
+  protected $profile = 'testing';
+
   public static function getInfo() {
     return array(
       'name' => 'Theme interface functionality',
@@ -1609,7 +1611,9 @@ class SystemThemeFunctionalTest extends DrupalWebTestCase {
   }
 
   function setUp() {
-    parent::setUp();
+    parent::setUp(array('block'));
+
+    $this->drupalCreateContentType(array('type' => 'page', 'name' => 'Basic page'));
 
     $this->admin_user = $this->drupalCreateUser(array('access administration pages', 'view the administration theme', 'administer themes', 'bypass node access', 'administer blocks'));
     $this->drupalLogin($this->admin_user);
@@ -1622,26 +1626,73 @@ class SystemThemeFunctionalTest extends DrupalWebTestCase {
   function testThemeSettings() {
     // Specify a filesystem path to be used for the logo.
     $file = current($this->drupalGetTestFiles('image'));
-    $fullpath = drupal_realpath($file->uri);
-    $edit = array(
-      'default_logo' => FALSE,
-      'logo_path' => $fullpath,
+    $supported_paths = array(
+      // Raw stream wrapper URIs are supported.
+      $file->uri,
+      // Relative paths within the public filesystem are supported.
+      file_uri_target($file->uri),
+      // Semi-absolute paths to public files are supported.
+      '/' . strtr($file->uri, array('public:/' => variable_get('file_public_path', conf_path() . '/files'))),
+      // Semi-absolute paths to arbitrary files are supported.
+      '/' . path_to_theme() . '/logo.png',
     );
-    $this->drupalPost('admin/appearance/settings', $edit, t('Save configuration'));
-    $this->drupalGet('node');
-    $this->assertRaw($fullpath, t('Logo path successfully changed.'));
+    foreach ($supported_paths as $path) {
+      $edit = array(
+        'default_logo' => FALSE,
+        'logo_path' => $path,
+      );
+      $this->drupalPost('admin/appearance/settings', $edit, t('Save configuration'));
+      $this->assertNoText('The custom logo path is invalid.');
+
+      $this->drupalGet('');
+      // Use semi-absolute path directly.
+      if ($path[0] === '/') {
+        // Do nothing.
+      }
+      // Prepend 'public://' for the relative file path within public
+      // filesystem case.
+      elseif (file_uri_scheme($path) === FALSE) {
+        $path = 'public://' . $path;
+      }
+      $elements = $this->xpath('//*[@id=:id]/img', array(':id' => 'logo'));
+      $this->assertEqual($elements[0]['src'], file_create_url($path));
+    }
+
+    $unsupported_paths = array(
+      // Stream wrapper URI to non-existing file.
+      'public://whatever.png',
+      // Relative path within the public filesystem to non-existing file.
+      'whatever.png',
+      // Semi-absolute paths to non-existing public file.
+      '/' . variable_get('file_public_path', conf_path() . '/files') . '/whatever.png',
+      // Semi-absolute paths to non-existing arbitrary file.
+      '/' . path_to_theme() . '/whatever.png',
+      // Absolute paths to any local file (even if it exists).
+      drupal_realpath($file->uri),
+    );
+    foreach ($unsupported_paths as $path) {
+      $edit = array(
+        'default_logo' => FALSE,
+        'logo_path' => $path,
+      );
+      $this->drupalPost('admin/appearance/settings', $edit, t('Save configuration'));
+      $this->assertText('The custom logo path is invalid.');
+    }
 
     // Upload a file to use for the logo.
-    $file = current($this->drupalGetTestFiles('image'));
     $edit = array(
       'default_logo' => FALSE,
       'logo_path' => '',
       'files[logo_upload]' => drupal_realpath($file->uri),
     );
-    $options = array();
-    $this->drupalPost('admin/appearance/settings', $edit, t('Save configuration'), $options);
-    $this->drupalGet('node');
-    $this->assertRaw($file->name, t('Logo file successfully uploaded.'));
+    $this->drupalPost('admin/appearance/settings', $edit, t('Save configuration'));
+
+    $fields = $this->xpath($this->constructFieldXpath('name', 'logo_path'));
+    $uploaded_filename = 'public://' . $fields[0]['value'];
+
+    $this->drupalGet('');
+    $elements = $this->xpath('//*[@id=:id]/img', array(':id' => 'logo'));
+    $this->assertEqual($elements[0]['src'], file_create_url($uploaded_filename));
   }
 
   /**
@@ -1700,20 +1751,20 @@ class SystemThemeFunctionalTest extends DrupalWebTestCase {
    * Test switching the default theme.
    */
   function testSwitchDefaultTheme() {
-    // Enable "stark" and set it as the default theme.
-    theme_enable(array('stark'));
+    // Enable Bartik and set it as the default theme.
+    theme_enable(array('bartik'));
     $this->drupalGet('admin/appearance');
-    $this->clickLink(t('Set default'), 1);
-    $this->assertTrue(variable_get('theme_default', '') == 'stark', t('Site default theme switched successfully.'));
+    $this->clickLink(t('Set default'));
+    $this->assertEqual(variable_get('theme_default', ''), 'bartik');
 
     // Test the default theme on the secondary links (blocks admin page).
     $this->drupalGet('admin/structure/block');
-    $this->assertText('Stark(' . t('active tab') . ')', t('Default local task on blocks admin page is the default theme.'));
-    // Switch back to Bartik and test again to test that the menu cache is cleared.
+    $this->assertText('Bartik(' . t('active tab') . ')', t('Default local task on blocks admin page is the default theme.'));
+    // Switch back to Stark and test again to test that the menu cache is cleared.
     $this->drupalGet('admin/appearance');
     $this->clickLink(t('Set default'), 0);
     $this->drupalGet('admin/structure/block');
-    $this->assertText('Bartik(' . t('active tab') . ')', t('Default local task on blocks admin page has changed.'));
+    $this->assertText('Stark(' . t('active tab') . ')', t('Default local task on blocks admin page has changed.'));
   }
 }