diff --git "a/C:\\Users\\Julien\\AppData\\Local\\Temp\\conE8EC.tmp\\content_types-HEAD-left.inc" "b/D:\\smartGit\\drupal\\modules\\node\\content_types.inc"
index 7442949..2ceac54 100644
--- "a/C:\\Users\\Julien\\AppData\\Local\\Temp\\conE8EC.tmp\\content_types-HEAD-left.inc"
+++ "b/D:\\smartGit\\drupal\\modules\\node\\content_types.inc"
@@ -232,9 +232,19 @@ function node_type_form_validate($form, &$form_state) {
     if (!preg_match('!^[a-z0-9_]+$!', $type->type)) {
       form_set_error('type', t('The machine-readable name must contain only lowercase letters, numbers, and underscores.'));
     }
+    // No content type should have a type value equal to the orig_type value 
+    // of another content type.
+    $invalid_type = FALSE;
+    $infos = node_get_types();
+    foreach ($infos as $info) {
+      if ($type->type == $info->orig_type) {
+        $invalid_type = TRUE;
+        break;
+      }
+    }
     // 'theme' conflicts with theme_node_form().
     // '0' is invalid, since elsewhere we check it using empty().
-    if (in_array($type->type, array('0', 'theme'))) {
+    if (in_array($type->type, array('0', 'theme')) || $invalid_type) {
       form_set_error('type', t("Invalid machine-readable name. Please enter a name other than %invalid.", array('%invalid' => $type->type)));
     }
   }