Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 23244)
+++ wp-includes/functions.php	(working copy)
@@ -925,7 +925,7 @@
 function nocache_headers() {
 	$headers = wp_get_nocache_headers();
 	foreach( $headers as $name => $field_value )
-		@header("{$name}: {$field_value}");
+		@header( "$name:" . ( strlen( $field_value ) ? " $field_value" : '' ) );
 	if ( empty( $headers['Last-Modified'] ) && function_exists( 'header_remove' ) )
 		@header_remove( 'Last-Modified' );
 }
Index: wp-includes/class-wp.php
===================================================================
--- wp-includes/class-wp.php	(revision 23244)
+++ wp-includes/class-wp.php	(working copy)
@@ -379,7 +379,7 @@
 		if ( ! empty( $status ) )
 			status_header( $status );
 		foreach( (array) $headers as $name => $field_value )
-			@header("{$name}: {$field_value}");
+			@header( "$name:" . ( strlen( $field_value ) ? " $field_value" : '' ) );
 
 		if ( isset( $headers['Last-Modified'] ) && empty( $headers['Last-Modified'] ) && function_exists( 'header_remove' ) )
 			@header_remove( 'Last-Modified' );