diff --git a/lib/class.js b/lib/class.js
index cfae254..9933fdf 100644
--- a/lib/class.js
+++ b/lib/class.js
@@ -790,21 +790,19 @@ function attachPropInit( prototype, properties, members )
             parent_init.call( this, true );
         }
 
+        // this will return our property proxy, if supported by our environment,
+        // otherwise just a normal object with everything merged in
         var inst_props = propobj.createPropProxy(
             this, class_instance[ this.__iid ], properties[ 'public' ]
         );
 
-        // use whatever was returned by the property proxy (which may not be a
-        // proxy, depending on JS engine support)
-        class_instance[ this.__iid ] = inst_props;
-
         // if we're inheriting, perform a setup that doesn't include everything
         // that we don't want (e.g. private properties)
         var setup = ( inherit )
             ? propobj.setupInherited
             : propobj.setup
         ;
-        setup( inst_props, properties, members );
+        class_instance[ this.__iid ] = setup( inst_props, properties, members );
     });
 }
 
diff --git a/lib/propobj.js b/lib/propobj.js
index c60d431..5e25e91 100644
--- a/lib/propobj.js
+++ b/lib/propobj.js
@@ -39,7 +39,7 @@ var util = require( './util' ),
  * @param  {Object}   properties  properties to copy
  * @param  {Object=}  methods     methods to copy
  *
- * @return  {undefined}
+ * @return  {Object}  dest
  */
 exports.setupInherited = function( dest, properties, methods )
 {
@@ -47,27 +47,41 @@ exports.setupInherited = function( dest, properties, methods )
     // ensure we're not sharing references to prototype values
     doSetup( dest, properties[ 'public' ] );
     doSetup( dest, properties[ 'protected' ], methods[ 'protected'] );
+
+    return dest;
 };
 
 
 /**
  * Sets up properties (non-inheriting)
  *
- * This includes all members (including private).
+ * This includes all members (including private). Private members will be set up
+ * in a separate object, so that they can be easily removed from the mix. That
+ * object will include the destination object in the prototype, so that the
+ * access should be transparent. This object is returned.
  *
  * @param  {Object}   dest        destination object
  * @param  {Object}   properties  properties to copy
  * @param  {Object=}  methods     methods to copy
  *
- * @return  {undefined}
+ * @return  {Object}  object containing private members and dest as prototype
  */
 exports.setup = function( dest, properties, methods )
 {
+    // this constructor is an extra layer atop of the destination object, which
+    // will contain the private methods
+    var obj_ctor = function() {};
+    obj_ctor.prototype = dest;
+
+    var obj = new obj_ctor();
+
     // first, set up the public and protected members
     exports.setupInherited( dest, properties, methods );
 
     // then add the private parts
-    doSetup( dest, properties[ 'private' ], methods[ 'private' ] );
+    doSetup( obj, properties[ 'private' ], methods[ 'private' ] );
+
+    return obj;
 };
 
 
diff --git a/test/perf/perf-class-invoke-method.js b/test/perf/perf-class-invoke-method.js
index bc8b5b8..2a97355 100644
--- a/test/perf/perf-class-invoke-method.js
+++ b/test/perf/perf-class-invoke-method.js
@@ -13,6 +13,10 @@
  *   - Protected and private methods internally should be accessed fairly
  *     quickly since, like public methods externally, they are first on the
  *     prototype chain.
+ *     - Protected members will be accessed more slowly than private members,
+ *       because they are one step lower on the prototype chain. Future versions
+ *       will remove this performance hit if the Class contains no private
+ *       members.
  *
  *  Copyright (C) 2010 Mike Gerwitz
  *