diff --git a/httpx/_models.py b/httpx/_models.py
index bd1ef638..bf3ac24e 100644
--- a/httpx/_models.py
+++ b/httpx/_models.py
@@ -918,8 +918,6 @@ class Response:
         # the client will set `response.next_request`.
         self.next_request: typing.Optional[Request] = None
 
-        self.call_next: typing.Optional[typing.Callable] = None
-
         self.extensions = {} if extensions is None else extensions
         self.history = [] if history is None else list(history)