Index: src/wp-admin/includes/update-core.php
===================================================================
--- src/wp-admin/includes/update-core.php	(revision 43808)
+++ src/wp-admin/includes/update-core.php	(working copy)
@@ -814,6 +814,7 @@
 	'themes/twentyfifteen/'   => '4.1',
 	'themes/twentysixteen/'   => '4.4',
 	'themes/twentyseventeen/' => '4.7',
+	'themes/twentynineteen/'  => '5.0',
 );
 
 /**
Index: src/wp-includes/class-wp-theme.php
===================================================================
--- src/wp-includes/class-wp-theme.php	(revision 43808)
+++ src/wp-includes/class-wp-theme.php	(working copy)
@@ -55,6 +55,7 @@
 		'twentyfifteen'   => 'Twenty Fifteen',
 		'twentysixteen'   => 'Twenty Sixteen',
 		'twentyseventeen' => 'Twenty Seventeen',
+		'twentynineteen'  => 'Twenty Nineteen',
 	);
 
 	/**
Index: src/wp-includes/default-constants.php
===================================================================
--- src/wp-includes/default-constants.php	(revision 43808)
+++ src/wp-includes/default-constants.php	(working copy)
@@ -358,6 +358,6 @@
 	 * @see WP_Theme::get_core_default_theme()
 	 */
 	if ( !defined('WP_DEFAULT_THEME') )
-		define( 'WP_DEFAULT_THEME', 'twentyseventeen' );
+		define( 'WP_DEFAULT_THEME', 'twentynineteen' );
 
 }
Index: tests/phpunit/tests/theme.php
===================================================================
--- tests/phpunit/tests/theme.php	(revision 43808)
+++ tests/phpunit/tests/theme.php	(working copy)
@@ -11,6 +11,7 @@
 	protected $default_themes = array(
 		'twentyten', 'twentyeleven', 'twentytwelve', 'twentythirteen',
 		'twentyfourteen', 'twentyfifteen', 'twentysixteen', 'twentyseventeen',
+		'twentynineteen',
 	);
 
 	function setUp() {