diff --git a/klein.php b/klein.php
index 2c4d43e..13a36bc 100644
--- a/klein.php
+++ b/klein.php
@@ -22,6 +22,7 @@ class Klein {
             ["{% endfor %}", "endforeach;"],
             ["{% ifset+:var %}", "if(isset(#1s)):"],
             ["{% if+:var %}", "if(isset(#1s) && #1s):"],
+            ["{% if+:id \(( :var (, :var )*)?\) %}", "if(macro_#1(#2s)):"],
             ["{% unless+:var %}", "if(!(isset(#1s) && #1s)):"],
             ["{% else %}", "else:"],
             ["{% endif %}", "endif;"],