diff --git a/client/doc/roles/tl.py b/client/doc/roles/tl.py
index 683441bd..f48c0a18 100644
--- a/client/doc/roles/tl.py
+++ b/client/doc/roles/tl.py
@@ -1,3 +1,4 @@
+# type: ignore
 from docutils import nodes, utils
 from docutils.parsers.rst.roles import set_classes
 
diff --git a/client/src/telethon/_impl/mtsender/sender.py b/client/src/telethon/_impl/mtsender/sender.py
index d3ade99a..52589214 100644
--- a/client/src/telethon/_impl/mtsender/sender.py
+++ b/client/src/telethon/_impl/mtsender/sender.py
@@ -247,7 +247,7 @@ class Sender:
                     if isinstance(ret, bytes):
                         assert len(ret) >= 4
                     elif isinstance(ret, RpcError):
-                        ret.caused_by = struct.unpack_from("<I", req.body)[0]
+                        ret._caused_by = struct.unpack_from("<I", req.body)[0]
                         raise ret
                     elif isinstance(ret, BadMessage):
                         # TODO test that we resend the request