diff --git a/tests/unit/test_vcr.py b/tests/unit/test_vcr.py
index a17535f..7150f15 100644
--- a/tests/unit/test_vcr.py
+++ b/tests/unit/test_vcr.py
@@ -283,6 +283,8 @@ class TestVCRClass(VCR().test_case()):
 
     def no_decoration(self):
         assert httplib.HTTPConnection == _HTTPConnection
+        self.test_dynamically_added()
+        assert httplib.HTTPConnection == _HTTPConnection
 
     def test_one(self):
         with force_reset():
@@ -293,3 +295,11 @@ class TestVCRClass(VCR().test_case()):
 
     def test_two(self):
         assert httplib.HTTPConnection != _HTTPConnection
+
+
+def test_dynamically_added(self):
+    assert httplib.HTTPConnection != _HTTPConnection
+
+
+TestVCRClass.test_dynamically_added = test_dynamically_added
+del test_dynamically_added
diff --git a/vcr/util.py b/vcr/util.py
index 9a44f9b..dd66320 100644
--- a/vcr/util.py
+++ b/vcr/util.py
@@ -98,13 +98,24 @@ def auto_decorate(
     decorator,
     predicate=lambda name, value: isinstance(value, types.FunctionType)
 ):
+    def maybe_decorate(attribute, value):
+        if predicate(attribute, value):
+            value = decorator(value)
+        return value
+
     class DecorateAll(type):
 
+        def __setattr__(cls, attribute, value):
+            return super(DecorateAll, cls).__setattr__(
+                attribute, maybe_decorate(attribute, value)
+            )
+
         def __new__(cls, name, bases, attributes_dict):
-            for attribute, value in attributes_dict.items():
-                if predicate(attribute, value):
-                    attributes_dict[attribute] = decorator(value)
+            new_attributes_dict = dict(
+                (attribute, maybe_decorate(attribute, value))
+                for attribute, value in attributes_dict.items()
+            )
             return super(DecorateAll, cls).__new__(
-                cls, name, bases, attributes_dict
+                cls, name, bases, new_attributes_dict
             )
     return DecorateAll