Index: wp-includes/classes.php
===================================================================
--- wp-includes/classes.php	(revision 15452)
+++ wp-includes/classes.php	(working copy)
@@ -376,6 +376,9 @@
 		foreach( (array) $headers as $name => $field_value )
 			@header("{$name}: {$field_value}");
 
+		if ( $_SERVER['REQUEST_METHOD'] == 'HEAD' && apply_filters( 'exit_on_http_head', true ) )
+			$exit_required = true;
+
 		if ($exit_required)
 			exit();