diff --git a/jackd/engine.c b/jackd/engine.c
--- a/jackd/engine.c
+++ b/jackd/engine.c
@@ -1615,6 +1615,10 @@ jack_engine_new (int realtime, int rtpri
 	engine->feedbackcount = 0;
 	engine->wait_pid = wait_pid;
 	engine->nozombies = nozombies;
+
+#ifndef JACK_USE_MACH_THREADS
+	engine->watchdog_thread = 0;
+#endif
 
 	jack_engine_reset_rolling_usecs (engine);
 	engine->max_usecs = 0.0f;