diff --git a/lib/output.js b/lib/output.js
index 42b3aad9..b99bfa63 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -72,8 +72,13 @@ function OutputStream(options) {
     function to_ascii(str) {
         return str.replace(/[\u0080-\uffff]/g, function(ch) {
             var code = ch.charCodeAt(0).toString(16);
-            while (code.length < 4) code = "0" + code;
-            return "\\u" + code;
+            if (code.length <= 2) {
+                while (code.length < 2) code = "0" + code;
+                return "\\x" + code;
+            } else {
+                while (code.length < 4) code = "0" + code;
+                return "\\u" + code;
+            }
         });
     };