diff --git a/wp-admin/includes/class-wp-upgrader.php b/wp-admin/includes/class-wp-upgrader.php
index 32e74c0ecd..2ab5e002a1 100644
--- a/wp-admin/includes/class-wp-upgrader.php
+++ b/wp-admin/includes/class-wp-upgrader.php
@@ -399,9 +399,13 @@ class Plugin_Upgrader extends WP_Upgrader {
 					'hook_extra' => array()
 					));
 
+		if ( ! $this->result || is_wp_error($this->result) )
+			return $this->result;
+
 		// Force refresh of plugin update information
 		delete_site_transient('update_plugins');
 
+		return true;
 	}
 
 	function upgrade($plugin) {
@@ -646,10 +650,7 @@ class Theme_Upgrader extends WP_Upgrader {
 		// Force refresh of theme update information
 		delete_site_transient('update_themes');
 
-		if ( empty($result['destination_name']) )
-			return false;
-		else
-			return $result['destination_name'];
+		return true;
 	}
 
 	function upgrade($theme) {
diff --git a/wp-admin/update.php b/wp-admin/update.php
index cbaee95859..a37f05060a 100644
--- a/wp-admin/update.php
+++ b/wp-admin/update.php
@@ -138,9 +138,10 @@ if ( isset($_GET['action']) ) {
 		$type = 'upload'; //Install plugin type, From Web or an Upload.
 
 		$upgrader = new Plugin_Upgrader( new Plugin_Installer_Skin( compact('type', 'title', 'nonce', 'url') ) );
-		$upgrader->install( $file_upload->package );
+		$result = $upgrader->install( $file_upload->package );
 
-		$file_upload->cleanup();
+		if ( $result || is_wp_error($result) )
+			$file_upload->cleanup();
 
 		include(ABSPATH . 'wp-admin/admin-footer.php');
 
@@ -242,9 +243,10 @@ if ( isset($_GET['action']) ) {
 		$type = 'upload'; //Install plugin type, From Web or an Upload.
 
 		$upgrader = new Theme_Upgrader( new Theme_Installer_Skin( compact('type', 'title', 'nonce', 'url') ) );
-		$upgrader->install( $file_upload->package );
+		$result = $upgrader->install( $file_upload->package );
 
-		$file_upload->cleanup();
+		if ( $result || is_wp_error($result) )
+			$file_upload->cleanup();
 
 		include(ABSPATH . 'wp-admin/admin-footer.php');