diff --git a/lib/propmangle.js b/lib/propmangle.js
index 44902bca..105dc813 100644
--- a/lib/propmangle.js
+++ b/lib/propmangle.js
@@ -78,6 +78,7 @@ function find_builtins() {
 }
 
 function mangle_properties(ast, options) {
+    console.log(options);
     options = defaults(options, {
         reserved : null,
         cache : null,
@@ -227,7 +228,7 @@ function mangle_properties(ast, options) {
                 // (filled with quoted properties when ignore_quoted set). Make sure we add this
                 // check so we don't collide with a quoted name.
                 do {
-                    mangled = base54(++cache.cname);
+                    mangled = options.prefix + base54(++cache.cname);
                 } while (!can_mangle(mangled) || (ignore_quoted && mangled in ignored));
             }