Index: modules/locale/locale.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/locale/locale.module,v
retrieving revision 1.293
diff -u -p -r1.293 locale.module
--- modules/locale/locale.module	12 May 2010 08:26:14 -0000	1.293
+++ modules/locale/locale.module	1 Jul 2010 08:40:20 -0000
@@ -961,7 +961,7 @@ function locale_block_view($type) {
  */
 function locale_url_outbound_alter(&$path, &$options, $original_path) {
   // Only modify internal URLs.
-  if (!$options['external']) {
+  if (!$options['external'] && drupal_multilingual()) {
     static $callbacks;
 
     if (!isset($callbacks)) {
Index: modules/path/path.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/path/path.test,v
retrieving revision 1.35
diff -u -p -r1.35 path.test
--- modules/path/path.test	26 Mar 2010 12:37:30 -0000	1.35
+++ modules/path/path.test	1 Jul 2010 08:47:17 -0000
@@ -251,10 +251,9 @@ class PathLanguageTestCase extends Drupa
 
     $this->drupalPost('admin/config/regional/language/add', $edit, t('Add language'));
 
-    // Set language negotiation to "Path prefix with fallback".
-    include_once DRUPAL_ROOT . '/includes/locale.inc';
-    variable_set('language_negotiation_' . LANGUAGE_TYPE_CONTENT, locale_language_negotiation_info());
-    variable_set('locale_language_negotiation_url_part', LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX);
+    // Enable URL language detection and selection.
+    $edit = array('language[enabled][locale-url]' => 1);
+    $this->drupalPost('admin/config/regional/language/configure', $edit, t('Save settings'));
 
     // Force inclusion of language.inc.
     drupal_language_initialize();
@@ -286,8 +285,10 @@ class PathLanguageTestCase extends Drupa
     $langcode = 'fr';
     $edit["body[$langcode][0][value]"] = $this->randomName();
     $langcode = LANGUAGE_NONE;
+    $path_alias = $this->randomName();
+
     $edit["title"] = $this->randomName();
-    $edit['path[alias]'] = $this->randomName();
+    $edit['path[alias]'] = $path_alias;
     $this->drupalPost(NULL, $edit, t('Save'));
 
     // Clear the path lookup cache.
@@ -298,14 +299,28 @@ class PathLanguageTestCase extends Drupa
     $this->assertTrue(($french_node), 'Node found in database.');
 
     // Confirm that the alias works.
-    $this->drupalGet('fr/' . $edit['path[alias]']);
+    $this->drupalGet("fr/$path_alias");
     $this->assertText($french_node->title, 'Alias for French translation works.');
 
     // Confirm that the alias is returned by url().
     drupal_static_reset('language_list');
     $languages = language_list();
     $url = url('node/' . $french_node->nid, array('language' => $languages[$french_node->language]));
-    $this->assertTrue(strpos($url, $edit['path[alias]']), t('URL contains the path alias.'));
+    $this->assertTrue(strpos($url, $path_alias), t('URL contains the path alias.'));
+
+    // Confirm that path aliases are not prefixed when just one language is
+    // enabled.
+    $edit = array('site_default' => 'fr');
+    $this->drupalPost('admin/config/regional/language', $edit, t('Save configuration'));
+    // Perform an additional POST here as first we have to change the default
+    // language and only after we can disable the former one.
+    $edit = array('enabled[en]' => FALSE);
+    $this->drupalPost('admin/config/regional/language', $edit, t('Save configuration'));
+    $this->assertFalse(drupal_multilingual(), t('English language disabled.'));
+    // Use an unprefixed alias to retrieve the node page and check that it does
+    // not contain prefixed URLs.
+    $this->drupalGet($path_alias);
+    $this->assertNoRaw("fr/$path_alias", t('Path alias prefixes are disabled when a single language is enabled.'));
   }
 }
 
Index: modules/translation/translation.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/translation/translation.module,v
retrieving revision 1.80
diff -u -p -r1.80 translation.module
--- modules/translation/translation.module	6 Jun 2010 00:24:16 -0000	1.80
+++ modules/translation/translation.module	1 Jul 2010 08:40:20 -0000
@@ -181,7 +181,7 @@ function translation_form_alter(&$form, 
  * is part of a translation set.
  */
 function translation_node_view($node, $view_mode) {
-  if (isset($node->tnid) && $translations = translation_node_get_translations($node->tnid)) {
+  if (isset($node->tnid) && drupal_multilingual() && $translations = translation_node_get_translations($node->tnid)) {
     $path = 'node/' . $node->nid;
     $links = language_negotiation_get_switch_links(LANGUAGE_TYPE_INTERFACE, $path);
     if (is_object($links)) {