diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 01fb5651dc2..875c6deb833 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -522,7 +522,7 @@ frame_sizeof(PyFrameObject *f)
 	nfrees = PyTuple_GET_SIZE(f->f_code->co_freevars);
 	extras = f->f_code->co_stacksize + f->f_code->co_nlocals +
 		 ncells + nfrees;
-	// subtract one as it is already included in PyFrameObject
+	/* subtract one as it is already included in PyFrameObject */
 	res = sizeof(PyFrameObject) + (extras-1) * sizeof(PyObject *);
 
 	return PyLong_FromSsize_t(res);