diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index 0de24f8..61ee42a 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -3918,7 +3918,7 @@
 }
 
 PyDoc_STRVAR(sizeof__doc__,
-"S.__sizeof__() -> size of S in bytes");
+"S.__sizeof__() -> size of S in memory, in bytes");
 
 static PyObject *
 string_sizeof(PyBytesObject *v)