diff --git a/Python/pystate.c b/Python/pystate.c
index a11f1622ecd4ab..09543add9dde1b 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -2196,6 +2196,7 @@ _PyThreadState_PushFrame(PyThreadState *tstate, size_t size)
 {
     assert(size < INT_MAX/sizeof(PyObject *));
     PyObject **base = tstate->datastack_top;
+    assert(base != NULL);
     PyObject **top = base + size;
     if (top >= tstate->datastack_limit) {
         base = push_chunk(tstate, (int)size);