diff --git a/src/wp-admin/includes/class-wp-upgrader-skins.php b/src/wp-admin/includes/class-wp-upgrader-skins.php
index 4f4ea063c0..3e9a5556b6 100644
--- a/src/wp-admin/includes/class-wp-upgrader-skins.php
+++ b/src/wp-admin/includes/class-wp-upgrader-skins.php
@@ -660,7 +660,7 @@ class Theme_Installer_Skin extends WP_Upgrader_Skin {
$install_actions = array();
if ( current_user_can( 'edit_theme_options' ) && current_user_can( 'customize' ) ) {
- $install_actions['preview'] .= '' . __( 'Live Preview' ) . '' . sprintf( __( 'Live Preview “%s”' ), $name ) . '';
+ $install_actions['preview'] = '' . __( 'Live Preview' ) . '' . sprintf( __( 'Live Preview “%s”' ), $name ) . '';
}
$install_actions['activate'] = '' . __( 'Activate' ) . '' . sprintf( __( 'Activate “%s”' ), $name ) . '';