diff --git a/src/wp-includes/theme.php b/src/wp-includes/theme.php
index ae12810961..a9f0e6ed8d 100644
--- a/src/wp-includes/theme.php
+++ b/src/wp-includes/theme.php
@@ -688,6 +688,8 @@ function switch_theme( $stylesheet ) {
 		set_theme_mod( 'sidebars_widgets', array( 'time' => time(), 'data' => $_sidebars_widgets ) );
 	}
 
+	$nav_menu_locations = get_theme_mod( 'nav_menu_locations' );
+
 	$old_theme  = wp_get_theme();
 	$new_theme = wp_get_theme( $stylesheet );
 
@@ -716,6 +718,9 @@ function switch_theme( $stylesheet ) {
 	// Migrate from the old mods_{name} option to theme_mods_{slug}.
 	if ( is_admin() && false === get_option( 'theme_mods_' . $stylesheet ) ) {
 		$default_theme_mods = (array) get_option( 'mods_' . $new_name );
+		if ( ! empty( $nav_menu_locations ) && empty( $default_theme_mods['nav_menu_locations'] ) ) {
+			$default_theme_mods['nav_menu_locations'] = $nav_menu_locations;
+		}
 		add_option( "theme_mods_$stylesheet", $default_theme_mods );
 	} else {
 		/*
@@ -726,6 +731,13 @@ function switch_theme( $stylesheet ) {
 		if ( 'wp_ajax_customize_save' === current_action() ) {
 			remove_theme_mod( 'sidebars_widgets' );
 		}
+
+		if ( ! empty( $nav_menu_locations ) ) {
+			$nav_mods = get_theme_mod( 'nav_menu_locations' );
+			if ( empty( $nav_mods ) ) {
+				set_theme_mod( 'nav_menu_locations', $nav_menu_locations );
+			}
+		}
 	}
 
 	update_option( 'theme_switched', $old_theme->get_stylesheet() );