diff --git a/moo/kernel/System.moo b/moo/kernel/System.moo
index 440d0c5..868b313 100644
--- a/moo/kernel/System.moo
+++ b/moo/kernel/System.moo
@@ -184,12 +184,15 @@ class System(Apex)
 			//(Processor _processById: 1) resume. //<---- i shouldn't do ths. but, this system causes VM assertion failure. fix it....
 			self.gcfin_should_exit := true.
 			self.gcfin_sem signal. // wake the gcfin process.
+
+			System _halting.
 		].
 	}
 
 	method(#class,#primitive) _getSig.
 	method(#class,#primitive) _getSigfd.
 	method(#class,#primitive) _setSig: signo.
+	method(#class,#primitive) _halting.
 
 	method(#class,#primitive) _popCollectable.
 	method(#class,#primitive) collectGarbage.
diff --git a/moo/lib/exec.c b/moo/lib/exec.c
index 5b55dfd..0b49bf1 100644
--- a/moo/lib/exec.c
+++ b/moo/lib/exec.c
@@ -3245,6 +3245,18 @@ static moo_pfrc_t pf_system_return_value_to_context (moo_t* moo, moo_mod_t* mod,
 	return MOO_PF_SUCCESS;
 }
 
+/* ------------------------------------------------------------------ */
+static moo_pfrc_t pf_system_halting (moo_t* moo, moo_mod_t* mod, moo_ooi_t nargs)
+{
+	moo_evtcb_t* cb;
+	for (cb = moo->evtcb_list; cb; cb = cb->next)
+	{
+		if (cb->halting) cb->halting (moo);
+	}
+	MOO_STACK_SETRETTORCV (moo, nargs);
+	return MOO_PF_SUCCESS;
+}
+
 /* ------------------------------------------------------------------ */
 static moo_pfrc_t pf_number_scale (moo_t* moo, moo_mod_t* mod, moo_ooi_t nargs)
 {
@@ -4351,6 +4363,7 @@ static pf_t pftab[] =
 	{ "System_getUint32",                      { moo_pf_system_get_uint32,                2, 2 } },
 	{ "System_getUint64",                      { moo_pf_system_get_uint64,                2, 2 } },
 	{ "System_getUint8",                       { moo_pf_system_get_uint8,                 2, 2 } },
+	{ "System_halting",                        { pf_system_halting,                       0, 0 } },
 	{ "System_log",                            { pf_system_log,                           2, MA } },
 	{ "System_malloc",                         { moo_pf_system_malloc,                    1, 1 } },
 	{ "System_malloc:",                        { moo_pf_system_malloc,                    1, 1 } },
diff --git a/moo/lib/moo.h b/moo/lib/moo.h
index fcb21b5..783d1cf 100644
--- a/moo/lib/moo.h
+++ b/moo/lib/moo.h
@@ -1255,13 +1255,14 @@ typedef struct moo_vmprim_t moo_vmprim_t;
 /* =========================================================================
  * CALLBACK MANIPULATION
  * ========================================================================= */
-typedef void (*moo_cbimpl_t) (moo_t* moo);
+typedef void (*moo_evtcb_impl_t) (moo_t* moo);
 
 typedef struct moo_evtcb_t moo_evtcb_t;
 struct moo_evtcb_t
 {
-	moo_cbimpl_t gc;
-	moo_cbimpl_t fini;
+	moo_evtcb_impl_t gc;
+	moo_evtcb_impl_t halting;
+	moo_evtcb_impl_t fini;
 
 	/* private below */
 	moo_evtcb_t*     prev;
diff --git a/moo/lib/std.c b/moo/lib/std.c
index 78483a8..8b3ed6d 100644
--- a/moo/lib/std.c
+++ b/moo/lib/std.c
@@ -380,6 +380,7 @@ struct xtn_t
 		pthread_mutex_t mtx;
 		pthread_cond_t cnd;
 		pthread_cond_t cnd2;
+		int halting;
 	#endif
 	} ev;
 };
@@ -2091,6 +2092,7 @@ static int vm_startup (moo_t* moo)
 	pthread_mutex_init (&xtn->ev.mtx, MOO_NULL);
 	pthread_cond_init (&xtn->ev.cnd, MOO_NULL);
 	pthread_cond_init (&xtn->ev.cnd2, MOO_NULL);
+	xtn->ev.halting = 0;
 
 	xtn->iothr.abort = 0;
 	xtn->iothr.up = 0;
@@ -2509,7 +2511,7 @@ static void vm_muxwait (moo_t* moo, const moo_ntime_t* dur, moo_vmprim_muxwait_c
 		ts.tv_nsec = ns.nsec;
 
 		pthread_mutex_lock (&xtn->ev.mtx);
-		if (xtn->ev.len <= 0)
+		if (xtn->ev.len <= 0 && !xtn->ev.halting)
 		{
 			/* the event buffer is still empty */
 			pthread_cond_timedwait (&xtn->ev.cnd2, &xtn->ev.mtx, &ts);
@@ -3688,6 +3690,19 @@ static void fini_moo (moo_t* moo)
 	unchain (moo);
 }
 
+static void halting_moo (moo_t* moo)
+{
+#if defined(USE_THREAD)
+	xtn_t* xtn = GET_XTN(moo);
+	xtn->ev.halting = 1;
+	pthread_mutex_unlock (&xtn->ev.mtx);
+	pthread_cond_signal (&xtn->ev.cnd2);
+	pthread_mutex_unlock (&xtn->ev.mtx);
+#else
+#	error NOT IMPLEMENTED YET
+#endif
+}
+
  moo_t* moo_openstd (moo_oow_t xtnsize, const moo_cfgstd_t* cfg, moo_errinf_t* errinfo)
 {
 	moo_t* moo;
@@ -3738,6 +3753,7 @@ static void fini_moo (moo_t* moo)
 
 	MOO_MEMSET (&evtcb, 0, MOO_SIZEOF(evtcb));
 	evtcb.fini = fini_moo;
+	evtcb.halting = halting_moo;
 	moo_regevtcb (moo, &evtcb);