diff --git a/wp-admin/includes/update-core.php b/wp-admin/includes/update-core.php
index e42162d0d4..7100524ea4 100644
--- a/wp-admin/includes/update-core.php
+++ b/wp-admin/includes/update-core.php
@@ -290,8 +290,16 @@ function update_core($from, $to) {
 
 	// Sanity check the unzipped distribution
 	apply_filters('update_feedback', __('Verifying the unpacked files…'));
-	if ( !$wp_filesystem->exists($from . '/wordpress/wp-settings.php') || !$wp_filesystem->exists($from . '/wordpress/wp-admin/admin.php') ||
-		!$wp_filesystem->exists($from . '/wordpress/wp-includes/functions.php') ) {
+	$distro = '';
+	$roots = array( '/wordpress', '/wordpress-mu' );
+	foreach( $roots as $root ) {
+		if ( $wp_filesystem->exists($from . $root . '/wp-settings.php') && $wp_filesystem->exists($from . $root . '/wp-admin/admin.php') &&
+			!$wp_filesystem->exists($from . $root . '/wp-includes/functions.php') ) {
+			$distro = $root;
+			break;
+		}
+	}
+	if ( !$distro ) {
 		$wp_filesystem->delete($from, true);
 		return new WP_Error('insane_distro', __('The update could not be unpacked') );
 	}
@@ -305,7 +313,7 @@ function update_core($from, $to) {
 	$wp_filesystem->put_contents($maintenance_file, $maintenance_string, FS_CHMOD_FILE);
 
 	// Copy new versions of WP files into place.
-	$result = copy_dir($from . '/wordpress', $to);
+	$result = copy_dir($from . $distro, $to);
 	if ( is_wp_error($result) ) {
 		$wp_filesystem->delete($maintenance_file);
 		$wp_filesystem->delete($from, true);