diff --git a/src/future/Future.php b/src/future/Future.php
--- a/src/future/Future.php
+++ b/src/future/Future.php
@@ -143,7 +143,7 @@
       $read_list,
       $write_list,
       $exceptfds,
-      $timeout,
+      $timeout_sec,
       $timeout_usec);
 
     if ($ok === false) {