Index: wp-includes/option.php
===================================================================
--- wp-includes/option.php	(revision 20831)
+++ wp-includes/option.php	(working copy)
@@ -229,7 +229,7 @@
 	$newvalue = apply_filters( 'pre_update_option_' . $option, $newvalue, $oldvalue );
 
 	// If the new and old values are the same, no need to update.
-	if ( $newvalue === $oldvalue )
+	if ( $newvalue === $oldvalue || $newvalue === sanitize_option( $option, $oldvalue ) )
 		return false;
 
 	if ( false === $oldvalue )