diff --git a/stdlib/multiprocessing/process.pyi b/stdlib/multiprocessing/process.pyi
index 249ff712e..32c22d19f 100644
--- a/stdlib/multiprocessing/process.pyi
+++ b/stdlib/multiprocessing/process.pyi
@@ -5,6 +5,7 @@ class BaseProcess:
     name: str
     daemon: bool
     authkey: bytes
+    _identity: Tuple[int, ...]  # undocumented
     def __init__(
         self,
         group: None = ...,