diff -u b/core/modules/config/src/Form/ConfigImportForm.php b/core/modules/config/src/Form/ConfigImportForm.php
--- b/core/modules/config/src/Form/ConfigImportForm.php
+++ b/core/modules/config/src/Form/ConfigImportForm.php
@@ -58,7 +58,7 @@
     $form['import_tarball'] = array(
       '#type' => 'file',
       '#title' => $this->t('Configuration archive'),
-      '#description' => $this->t('Allowed types: @extensions.', array('@extensions' => 'tar.gz tgz')),
+      '#description' => $this->t('Allowed types: @extensions.', array('@extensions' => 'tar.gz tgz tar.bz2')),
     );
 
     $form['submit'] = array(