diff -r 4f74452a11e5 Lib/plistlib.py
--- a/Lib/plistlib.py	Wed Apr 15 23:02:12 2015 -0400
+++ b/Lib/plistlib.py	Mon Apr 27 12:59:49 2015 +0200
@@ -341,7 +341,9 @@
 
     def add_object(self, value):
         if self.current_key is not None:
-            if not isinstance(self.stack[-1], type({})):
+            if isinstance(self.stack[-1], list):
+                # NOTE: ^^^ doesn't test for self._dict_type due to backward
+                #       compatibility concerns
                 raise ValueError("unexpected element at line %d" %
                                  self.parser.CurrentLineNumber)
             self.stack[-1][self.current_key] = value
@@ -350,7 +352,7 @@
             # this is the root object
             self.root = value
         else:
-            if not isinstance(self.stack[-1], type([])):
+            if not isinstance(self.stack[-1], list):
                 raise ValueError("unexpected element at line %d" %
                                  self.parser.CurrentLineNumber)
             self.stack[-1].append(value)
@@ -374,7 +376,9 @@
         self.stack.pop()
 
     def end_key(self):
-        if self.current_key or not isinstance(self.stack[-1], type({})):
+        if self.current_key or isinstance(self.stack[-1], list):
+            # NOTE: ^^^ doesn't test for self._dict_type due to backward
+            #       compatibility concerns
             raise ValueError("unexpected key at line %d" %
                              self.parser.CurrentLineNumber)
         self.current_key = self.get_data()
diff -r 4f74452a11e5 Lib/test/test_plistlib.py
--- a/Lib/test/test_plistlib.py	Wed Apr 15 23:02:12 2015 -0400
+++ b/Lib/test/test_plistlib.py	Mon Apr 27 12:59:49 2015 +0200
@@ -264,6 +264,22 @@
                     else:
                         self.assertEqual(list(pl2.keys()), ['b', 'a', 'c'])
 
+    def test_alternate_dicttype(self):
+        pl = {
+            'a': { 'b': 'c' },
+            'b': 4,
+            'c': [ 'x', 'y' ]
+        }
+
+        for fmt in ALL_FORMATS:
+            with self.subTest(fmt=fmt):
+                data = plistlib.dumps(pl, fmt=fmt)
+                pl2 = plistlib.loads(data, dict_type=collections.UserDict)
+                self.assertEqual(dict(pl), dict(pl2))
+
+                self.assertIsInstance(pl2, collections.UserDict)
+                self.assertIsInstance(pl2['a'], collections.UserDict)
+
     def test_keys_no_string(self):
         pl = { 42: 'aNumber' }