diff --git a/stdlib/sys/__init__.pyi b/stdlib/sys/__init__.pyi
index 9989a27b2..d65ddfe38 100644
--- a/stdlib/sys/__init__.pyi
+++ b/stdlib/sys/__init__.pyi
@@ -355,7 +355,11 @@ def set_int_max_str_digits(maxdigits: int) -> None: ...
 def get_int_max_str_digits() -> int: ...
 
 if sys.version_info >= (3, 12):
-    def getunicodeinternedsize() -> int: ...
+    if sys.version_info >= (3, 13):
+        def getunicodeinternedsize(*, _only_immortal: bool = False) -> int: ...
+    else:
+        def getunicodeinternedsize() -> int: ...
+
     def deactivate_stack_trampoline() -> None: ...
     def is_stack_trampoline_active() -> bool: ...
     # It always exists, but raises on non-linux platforms: