diff --git a/telegram/base.py b/telegram/base.py
index 3431396c9..65c43678e 100644
--- a/telegram/base.py
+++ b/telegram/base.py
@@ -57,12 +57,7 @@ class TelegramObject(object):
         data = dict()
 
         for key in iter(self.__dict__):
-            if key in ('bot',
-                       '_id_attrs',
-                       '_credentials',
-                       '_decrypted_credentials',
-                       '_decrypted_data',
-                       '_decrypted_secret'):
+            if key == 'bot' or key.startswith('_'):
                 continue
 
             value = self.__dict__[key]
diff --git a/tests/test_telegramobject.py b/tests/test_telegramobject.py
index 66f52dbfb..156c43b65 100644
--- a/tests/test_telegramobject.py
+++ b/tests/test_telegramobject.py
@@ -74,3 +74,12 @@ class TestTelegramObject(object):
 
         monkeypatch.setattr('telegram.TelegramObject.to_dict', lambda _: d)
         telegram_object.to_json()
+
+    def test_to_dict_private_attribute(self):
+        class TelegramObjectSubclass(TelegramObject):
+            def __init__(self):
+                self.a = 1
+                self._b = 2
+
+        subclass_instance = TelegramObjectSubclass()
+        assert subclass_instance.to_dict() == {'a': 1}