diff --git a/src/Theme_Command.php b/src/Theme_Command.php
index cac02679..19bf71b0 100644
--- a/src/Theme_Command.php
+++ b/src/Theme_Command.php
@@ -489,7 +489,7 @@ protected function filter_item_list( $items, $args ) {
 	 */
 	public function install( $args, $assoc_args ) {
 		if ( count( $args ) > 1 && Utils\get_flag_value( $assoc_args, 'activate', false ) ) {
-			WP_CLI::warning( sprintf( "Only this single theme will be activated: %s", end( $args ) ) );
+			WP_CLI::warning( sprintf( 'Only this single theme will be activated: %s', end( $args ) ) );
 			reset( $args );
 		}