Index: threadproc/unix/thread.c
===================================================================
--- threadproc/unix/thread.c	(revision 595807)
+++ threadproc/unix/thread.c	(working copy)
@@ -251,7 +251,11 @@
 APR_DECLARE(void) apr_thread_yield(void)
 {
 #ifdef HAVE_PTHREAD_YIELD
+#ifdef HAVE_ZOS_PTHREADS
+    pthread_yield(NULL);
+#else
     pthread_yield();
+#endif /* HAVE_ZOS_PTHREADS */
 #else
 #ifdef HAVE_SCHED_YIELD
     sched_yield();