diff --git a/telegram/ext/callbackcontext.py b/telegram/ext/callbackcontext.py
index 752bf14be..aeb3eb964 100644
--- a/telegram/ext/callbackcontext.py
+++ b/telegram/ext/callbackcontext.py
@@ -73,13 +73,31 @@ class CallbackContext(object):
             raise ValueError('CallbackContext should not be used with a non context aware '
                              'dispatcher!')
         self._dispatcher = dispatcher
-        self.chat_data = None
-        self.user_data = None
+        self._chat_data = None
+        self._user_data = None
         self.args = None
         self.matches = None
         self.error = None
         self.job = None
 
+    @property
+    def chat_data(self):
+        return self._chat_data
+
+    @chat_data.setter
+    def chat_data(self, value):
+        raise AttributeError("You can not assign a new value to chat_data, see "
+                             "https://git.io/fjxKe")
+
+    @property
+    def user_data(self):
+        return self._user_data
+
+    @user_data.setter
+    def user_data(self, value):
+        raise AttributeError("You can not assign a new value to user_data, see "
+                             "https://git.io/fjxKe")
+
     @classmethod
     def from_error(cls, update, error, dispatcher):
         self = cls.from_update(update, dispatcher)
@@ -94,9 +112,9 @@ class CallbackContext(object):
             user = update.effective_user
 
             if chat:
-                self.chat_data = dispatcher.chat_data[chat.id]
+                self._chat_data = dispatcher.chat_data[chat.id]
             if user:
-                self.user_data = dispatcher.user_data[user.id]
+                self._user_data = dispatcher.user_data[user.id]
         return self
 
     @classmethod
diff --git a/tests/test_callbackcontext.py b/tests/test_callbackcontext.py
index ce9b8b5df..2eefddaf8 100644
--- a/tests/test_callbackcontext.py
+++ b/tests/test_callbackcontext.py
@@ -105,3 +105,15 @@ class TestCallbackContext(object):
         callback_context.matches = ['test', 'blah']
 
         assert callback_context.match == 'test'
+
+    def test_data_assignment(self, cdp):
+        update = Update(0, message=Message(0, User(1, 'user', False), None, Chat(1, 'chat')))
+
+        callback_context = CallbackContext.from_update(update, cdp)
+
+        with pytest.raises(AttributeError):
+            callback_context.chat_data = {"test": 123}
+        with pytest.raises(AttributeError):
+            callback_context.user_data = {}
+        with pytest.raises(AttributeError):
+            callback_context.chat_data = "test"