Index: src/wp-includes/update.php
===================================================================
--- src/wp-includes/update.php	(revision 30373)
+++ src/wp-includes/update.php	(working copy)
@@ -648,6 +648,17 @@
 	}
 }
 
+/**
+ * Clear existing update caches for plugins, themes, and core.
+ *
+ * @since 4.1.0
+ */
+function _clear_update_transients() {
+	wp_clean_plugins_cache();
+	wp_clean_themes_cache();
+	delete_site_transient( 'update_core' );
+}
+
 if ( ( ! is_main_site() && ! is_network_admin() ) || ( defined( 'DOING_AJAX' ) && DOING_AJAX ) )
 	return;
 
@@ -662,6 +673,8 @@
 add_action( 'wp_update_plugins', 'wp_update_plugins' );
 add_action( 'upgrader_process_complete', 'wp_update_plugins', 10, 0 );
 
+add_action( 'update_option_WPLANG', '_clear_update_transients' , 10, 0 );
+
 add_action( 'load-themes.php', 'wp_update_themes' );
 add_action( 'load-update.php', 'wp_update_themes' );
 add_action( 'load-update-core.php', 'wp_update_themes' );