diff --git a/lib/libthr/thread/thr_private.h b/lib/libthr/thread/thr_private.h
index eb2632d9e9f8..ab64bf7a6c79 100644
--- a/lib/libthr/thread/thr_private.h
+++ b/lib/libthr/thread/thr_private.h
@@ -72,7 +72,7 @@ TAILQ_HEAD(mutex_queue, pthread_mutex);
 
 /* Output debug messages like this: */
 #define stdout_debug(args...)	_thread_printf(STDOUT_FILENO, ##args)
-#define stderr_debug(args...)	_thread_printf(STDOUT_FILENO, ##args)
+#define stderr_debug(args...)	_thread_printf(STDERR_FILENO, ##args)
 
 #ifdef _PTHREADS_INVARIANTS
 #define THR_ASSERT(cond, msg) do {	\