--- a/src/sage/cpython/cython_metaclass.h
+++ b/src/sage/cpython/cython_metaclass.h
@@ -66,7 +66,7 @@
         }
 
         /* Now, set t.__class__ to metaclass */
-        Py_TYPE(t) = metaclass;
+        Py_SET_TYPE(t, metaclass);
         PyType_Modified(t);
     }
     else
--- a/src/sage/symbolic/ginac/numeric.cpp
+++ b/src/sage/symbolic/ginac/numeric.cpp
@@ -52,7 +52,6 @@
 #define register
 #define PY_SSIZE_T_CLEAN
 #include <Python.h>
-#include <longintrepr.h>
 #include "flint/fmpz.h"
 #include "flint/fmpz_factor.h"
 
--- a/src/sage/libs/gmp/pylong.pyx
+++ b/src/sage/libs/gmp/pylong.pyx
@@ -32,7 +32,7 @@
 from .mpz cimport *
 
 cdef extern from *:
-    Py_ssize_t* Py_SIZE_PTR "&Py_SIZE"(object)
+    void Py_SET_SIZE(object, Py_ssize_t)
     int hash_bits """
         #ifdef _PyHASH_BITS
         _PyHASH_BITS         /* Python 3 */
@@ -57,10 +57,8 @@
     mpz_export(L.ob_digit, NULL,
             -1, sizeof(digit), 0, PyLong_nails, z)
     if mpz_sgn(z) < 0:
-        # Set correct size (use a pointer to hack around Cython's
-        # non-support for lvalues).
-        sizeptr = Py_SIZE_PTR(L)
-        sizeptr[0] = -pylong_size
+        # Set correct size
+        Py_SET_SIZE(L, -pylong_size)
     return L