Index: src/wp-content/themes/twentyfifteen/functions.php
===================================================================
--- src/wp-content/themes/twentyfifteen/functions.php	(revision 36674)
+++ src/wp-content/themes/twentyfifteen/functions.php	(working copy)
@@ -71,6 +71,7 @@
 	 * provide it for us.
 	 */
 	add_theme_support( 'title-tag' );
+	add_theme_support( 'site-logo', array( 'size' => 'large' ) );
 
 	/*
 	 * Enable support for Post Thumbnails on posts and pages.
Index: src/wp-content/themes/twentyfifteen/header.php
===================================================================
--- src/wp-content/themes/twentyfifteen/header.php	(revision 36674)
+++ src/wp-content/themes/twentyfifteen/header.php	(working copy)
@@ -28,6 +28,7 @@
 	<div id="sidebar" class="sidebar">
 		<header id="masthead" class="site-header" role="banner">
 			<div class="site-branding">
+				<?php the_site_logo(); ?>
 				<?php
 					if ( is_front_page() && is_home() ) : ?>
 						<h1 class="site-title"><a href="<?php echo esc_url( home_url( '/' ) ); ?>" rel="home"><?php bloginfo( 'name' ); ?></a></h1>