diff --git a/prettify/lang-yaml.js b/prettify/lang-yaml.js
index c38729b6..1f533d84 100644
--- a/prettify/lang-yaml.js
+++ b/prettify/lang-yaml.js
@@ -1,2 +1,2 @@
-var a=null;
+let a=null;
 PR.registerLangHandler(PR.createSimpleLexer([["pun",/^[:>?|]+/,a,":|>?"],["dec",/^%(?:YAML|TAG)[^\n\r#]+/,a,"%"],["typ",/^&\S+/,a,"&"],["typ",/^!\S*/,a,"!"],["str",/^"(?:[^"\\]|\\.)*(?:"|$)/,a,'"'],["str",/^'(?:[^']|'')*(?:'|$)/,a,"'"],["com",/^#[^\n\r]*/,a,"#"],["pln",/^\s+/,a," \t\r\n"]],[["dec",/^(?:---|\.\.\.)(?:[\n\r]|$)/],["pun",/^-/],["kwd",/^\w+:[\n\r ]/],["pln",/^\w+/]]),["yaml","yml"]);