Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 5419)
+++ wp-includes/functions.php	(working copy)
@@ -915,10 +915,15 @@
 	elseif ( 410 == $header )
 		$text = 'Gone';
 
+	$protocol = trim($_SERVER["SERVER_PROTOCOL"]);
+	if ( ('HTTP/1.1' != $protocol) && ('HTTP/1.0' != $protocol) )
+		$protocol = 'HTTP/1.1';
+	$status_header = "$protocol $header $text";
+	$status_header = apply_filters('status_header', $status_header, $header, $text, $protocol);
 	if ( version_compare(phpversion(), '4.3.0', '>=') )
-		@header("HTTP/1.1 $header $text", true, $header);
+		@header($status_header, true, $header);
 	else
-		@header("HTTP/1.1 $header $text");
+		@header($status_header);
 }
 
 function nocache_headers() {