diff --git a/lib/output.js b/lib/output.js
index 05f8b5d1..59556f5e 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -134,7 +134,7 @@ function OutputStream(options) {
 
     function make_string(str, quote) {
         var dq = 0, sq = 0;
-        str = str.replace(/[\\\b\f\n\r\v\t\x22\x27\u2028\u2029\0\ufeff\uffff]/g,
+        str = str.replace(/[\\\b\f\n\r\v\t\x1f\x22\x27\u2028\u2029\0\ufeff\uffff]/g,
           function(s, i){
             switch (s) {
               case '"': ++dq; return '"';
@@ -146,6 +146,7 @@ function OutputStream(options) {
               case "\b": return "\\b";
               case "\f": return "\\f";
               case "\x0B": return options.screw_ie8 ? "\\v" : "\\x0B";
+              case "\x1f": return "\\x1f";
               case "\u2028": return "\\u2028";
               case "\u2029": return "\\u2029";
               case "\ufeff": return "\\ufeff";