diff --git a/wp-admin/install.php b/wp-admin/install.php
index a846abb088..8fa704aa60 100644
--- a/wp-admin/install.php
+++ b/wp-admin/install.php
@@ -41,6 +41,8 @@ require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
 /** Load wpdb */
 require_once( ABSPATH . WPINC . '/wp-db.php' );
 
+nocache_headers();
+
 $step = isset( $_GET['step'] ) ? (int) $_GET['step'] : 0;
 
 /**
diff --git a/wp-admin/setup-config.php b/wp-admin/setup-config.php
index dfcd4edf9b..3ca3059d7c 100644
--- a/wp-admin/setup-config.php
+++ b/wp-admin/setup-config.php
@@ -34,6 +34,8 @@ require( ABSPATH . 'wp-settings.php' );
 
 require( ABSPATH . 'wp-admin/includes/upgrade.php' );
 
+nocache_headers();
+
 // Support wp-config-sample.php one level up, for the develop repo.
 if ( file_exists( ABSPATH . 'wp-config-sample.php' ) )
 	$config_file = file( ABSPATH . 'wp-config-sample.php' );
diff --git a/wp-includes/load.php b/wp-includes/load.php
index 043743e244..07f2283ab9 100644
--- a/wp-includes/load.php
+++ b/wp-includes/load.php
@@ -466,9 +466,14 @@ function wp_start_object_cache() {
  */
 function wp_not_installed() {
 	if ( is_multisite() ) {
-		if ( ! is_blog_installed() && ! defined( 'WP_INSTALLING' ) )
+		if ( ! is_blog_installed() && ! defined( 'WP_INSTALLING' ) ) {
+			nocache_headers();
+
 			wp_die( __( 'The site you have requested is not installed properly. Please contact the system administrator.' ) );
+		}
 	} elseif ( ! is_blog_installed() && false === strpos( $_SERVER['PHP_SELF'], 'install.php' ) && !defined( 'WP_INSTALLING' ) ) {
+		nocache_headers();
+
 		require( ABSPATH . WPINC . '/kses.php' );
 		require( ABSPATH . WPINC . '/pluggable.php' );
 		require( ABSPATH . WPINC . '/formatting.php' );