diff --git a/lib/scope.js b/lib/scope.js
index 950128d4d64..de0bd965744 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -249,6 +249,11 @@ AST_Scope.DEFMETHOD("next_mangled", function(options){
         // we must ensure that the mangled name does not shadow a name
         // from some parent scope that is referenced in this or in
         // inner scopes.
+
+        //bugfix: https://github.com/mishoo/UglifyJS2/issues/242
+        if(options.except.indexOf(m) !== -1){
+            continue;
+        }
         for (var i = ext.length; --i >= 0;) {
             var sym = ext[i];
             var name = sym.mangled_name || (sym.unmangleable(options) && sym.name);