Issue #19526: Exclude all new API from the stable ABI.
diff --git a/Include/pyhash.h b/Include/pyhash.h
index 83c9281..a7ca937 100644
--- a/Include/pyhash.h
+++ b/Include/pyhash.h
@@ -50,6 +50,7 @@
  * (*) The siphash member may not be available on 32 bit platforms without
  *     an unsigned int64 data type.
  */
+#ifndef Py_LIMITED_API
 typedef union {
     /* ensure 24 bytes */
     unsigned char uc[24];
@@ -76,6 +77,7 @@
     } expat;
 } _Py_HashSecret_t;
 PyAPI_DATA(_Py_HashSecret_t) _Py_HashSecret;
+#endif
 
 #ifdef Py_DEBUG
 PyAPI_DATA(int) _Py_HashSecret_Initialized;