diff --git a/sites/all/modules/contrib/stringoverrides/stringoverrides_migrate.admin.inc b/sites/all/modules/contrib/stringoverrides/stringoverrides_migrate.admin.inc
index 29d67f5..818b9e8 100644
--- a/sites/all/modules/contrib/stringoverrides/stringoverrides_migrate.admin.inc
+++ b/sites/all/modules/contrib/stringoverrides/stringoverrides_migrate.admin.inc
@@ -31,7 +31,9 @@ function stringoverrides_migrate_admin_import() {
  */
 function stringoverrides_migrate_admin_import_submit($form, &$form_state) {
   // Check if the file uploaded correctly
-  $file = file_save_upload('file');
+  $file = file_save_upload('file', array(
+    'file_validate_extensions' => array('po'),
+  ));
   if (!$file) {
     form_set_error('file', t('A file to import is required.'));
     return;