diff --git a/scripts/phutil_analyzer.php b/scripts/phutil_analyzer.php
index 5dd568a4..e091d09a 100755
--- a/scripts/phutil_analyzer.php
+++ b/scripts/phutil_analyzer.php
@@ -39,6 +39,7 @@ $builtin = array(
 
       'phutil_is_windows'   => true,
       'phutil_load_library' => true,
+      'phutil_is_hiphop_runtime' => true,
 
       // HPHP/i defines these functions as 'internal', but they are NOT
       // builtins and do not exist in vanilla PHP. Make sure we don't mark them