Issue #19526: Exclude all new API from the stable ABI.
diff --git a/Include/pystate.h b/Include/pystate.h
index 06af808..1f3465f 100644
--- a/Include/pystate.h
+++ b/Include/pystate.h
@@ -236,7 +236,9 @@
 /* Helper/diagnostic function - return 1 if the current thread
  * currently holds the GIL, 0 otherwise
  */
+#ifndef Py_LIMITED_API
 PyAPI_FUNC(int) PyGILState_Check(void);
+#endif
 
 #endif   /* #ifdef WITH_THREAD */