diff --git a/lib/propobj.js b/lib/propobj.js
index 7ea372d..38d59e6 100644
--- a/lib/propobj.js
+++ b/lib/propobj.js
@@ -46,12 +46,17 @@ var util = require( './util' ),
  */
 exports.setup = function( dest, properties, methods )
 {
+    var obj = dest;
+
     // 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;
+    if ( defprop )
+    {
+        var obj_ctor = function() {};
+        obj_ctor.prototype = dest;
 
-    var obj = new obj_ctor();
+        obj = new obj_ctor();
+    }
 
     // initialize each of the properties for this instance to
     // ensure we're not sharing references to prototype values
diff --git a/test/test-class-visibility.js b/test/test-class-visibility.js
index 2179874..72c72a3 100644
--- a/test/test-class-visibility.js
+++ b/test/test-class-visibility.js
@@ -479,6 +479,13 @@ var common  = require( './common' ),
  */
 ( function testParentsShouldNotHaveAccessToPrivateMembersOfSubtypes()
 {
+    // browsers that do not support the property proxy will not support
+    // encapsulating properties
+    if ( !( propobj.supportsPropProxy() ) )
+    {
+        return;
+    }
+
     // property
     assert.equal(
         sub_foo.nonOverrideGetProp( '_pfoo' ),