Index: src/wp-includes/theme.php
===================================================================
--- src/wp-includes/theme.php	(revision 27296)
+++ src/wp-includes/theme.php	(working copy)
@@ -1204,12 +1204,13 @@
  * @since 3.0.0
  *
  * @param string|array $header The header string id (key of array) to remove, or an array thereof.
- * @return True on success, false on failure.
+ * @return bool True on success, false on failure.
  */
 function unregister_default_headers( $header ) {
 	global $_wp_default_headers;
 	if ( is_array( $header ) ) {
-		array_map( 'unregister_default_headers', $header );
+		$results = array_map( 'unregister_default_headers', $header ); 
+		return ! in_array( false, $results, true );
 	} elseif ( isset( $_wp_default_headers[ $header ] ) ) {
 		unset( $_wp_default_headers[ $header ] );
 		return true;