Index: wp-includes/deprecated.php
===================================================================
--- wp-includes/deprecated.php	(revision 21036)
+++ wp-includes/deprecated.php	(working copy)
@@ -3114,6 +3114,13 @@
 		'AuthorName' => $theme->display('Author', false, false),
 	);
 
+	if ( $extra_headers = apply_filters( 'extra_theme_headers', array() ) ) {
+		$extra_headers = array_combine( $extra_headers, $extra_headers ); // keys equal values
+		foreach ( $extra_headers as $key )
+			$extra_headers[ $key ] = $theme->get( $key );
+		$theme_data = array_merge( $extra_headers, $theme_data );
+	}
+
 	return $theme_data;
 }