Py_ssize_t is defined regardless of HAVE_LONG_LONG.  Will backport
diff --git a/Misc/NEWS b/Misc/NEWS
index a79810d..123e911 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@
 Core and builtins
 -----------------
 
+- Py_ssize_t fields work in structmember when HAVE_LONG_LONG is not defined.
+
 - PEP 3123: Provide forward compatibility with Python 3.0, while keeping
   backwards compatibility. Add Py_Refcnt, Py_Type, Py_Size, and
   PyVarObject_HEAD_INIT.