diff -urp src.old/winsup/cygwin/thread.cc src/winsup/cygwin/thread.cc
--- src.old/winsup/cygwin/thread.cc	Wed Sep 25 09:22:03 2002
+++ src/winsup/cygwin/thread.cc	Wed Sep 25 09:55:09 2002
@@ -248,7 +248,7 @@ pthread::destructor (void *value)
 {
   pthread *thread = (pthread *) value;
   /* cleanup thread if thread is detached and not joined */
-  if (thread && __pthread_equal(&thread->joiner, &thread))
+  if (isGoodObject (&thread) && __pthread_equal(&thread->joiner, &thread))
     delete thread;
 }