diff --git a/acorn.js b/acorn.js
index 979b9317de..c6341b605e 100644
--- a/acorn.js
+++ b/acorn.js
@@ -1269,7 +1269,7 @@
   function readWord() {
     var word = readWord1();
     var type = _name;
-    if (!containsEsc && isKeyword(word))
+    if ((options.ecmaVersion >= 6 || !containsEsc) && isKeyword(word))
       type = keywordTypes[word];
     return finishToken(type, word);
   }