diff --git modules/update/update.manager.inc modules/update/update.manager.inc
index 4f55b1b..d77728f 100644
--- modules/update/update.manager.inc
+++ modules/update/update.manager.inc
@@ -645,7 +645,8 @@ function update_manager_install_form_submit($form, &$form_state) {
     return;
   }
   // Unfortunately, we can only use the directory name for this. :(
-  $project = drupal_substr($files[0], 0, -1);
+  $project = explode('/', $files[0], 2);
+  $project = $project[0];
 
   $archive_errors = update_manager_archive_verify($project, $local_cache, $directory);
   if (!empty($archive_errors)) {