diff --git a/core/net/mac/contikimac.c b/core/net/mac/contikimac.c
index f1b162a44..510f59451 100644
--- a/core/net/mac/contikimac.c
+++ b/core/net/mac/contikimac.c
@@ -28,7 +28,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: contikimac.c,v 1.20 2010/03/31 11:54:38 adamdunkels Exp $
+ * $Id: contikimac.c,v 1.21 2010/03/31 20:27:15 adamdunkels Exp $
  */
 
 /**
@@ -99,13 +99,15 @@ struct announcement_msg {
 #define CYCLE_TIME (RTIMER_ARCH_SECOND / MAC_CHANNEL_CHECK_RATE)
 #endif
 
-#define MAX_PHASE_STROBES                  12
+#define MAX_PHASE_STROBE_TIME              RTIMER_ARCH_SECOND / 20
 
 #define CCA_COUNT_MAX 2
 #define CCA_CHECK_TIME                     RTIMER_ARCH_SECOND / 8192
 #define CCA_SLEEP_TIME                     RTIMER_ARCH_SECOND / 2000 //+ CCA_CHECK_TIME
 #define CHECK_TIME                         (CCA_COUNT_MAX * (CCA_CHECK_TIME + CCA_SLEEP_TIME))
 
+#define STROBE_TIME                        (CYCLE_TIME + 2 * CHECK_TIME)
+
 #define STREAM_CCA_COUNT                   (CYCLE_TIME / (CCA_SLEEP_TIME + CCA_CHECK_TIME) - CCA_COUNT_MAX)
 
 #define GUARD_TIME                         7 * CHECK_TIME
@@ -130,9 +132,6 @@ struct announcement_msg {
    cycle. */
 #define ANNOUNCEMENT_TIME (random_rand() % (ANNOUNCEMENT_PERIOD))
 
-#define STROBE_WAIT_TIME (RTIMER_ARCH_SECOND / 600)
-
-#define STROBE_TIME (CYCLE_TIME + 2 * CHECK_TIME)
 
 #define ACK_LEN 3
 
@@ -415,6 +414,12 @@ parse_announcements(void)
      }
      printf("\n"); */
 
+  if(adata.num / sizeof(struct announcement_data) > sizeof(struct announcement_msg)) {
+    /* Sanity check. The number of announcements is too large -
+       corrupt packet has been received. */
+    return 0;
+  }
+
   for(i = 0; i < adata.num; ++i) {
     /*    printf("%d.%d: announcement %d: %d\n",
        rimeaddr_node_addr.u8[0], rimeaddr_node_addr.u8[1],
@@ -657,7 +662,7 @@ send_packet(mac_callback_t mac_callback, void *mac_callback_ptr)
 
     watchdog_periodic();
     
-    if(is_known_receiver && strobes > MAX_PHASE_STROBES) {
+    if(is_known_receiver && !RTIMER_CLOCK_LT(RTIMER_NOW(), t0 + MAX_PHASE_STROBE_TIME)) {
       break;
     }
     
@@ -692,7 +697,6 @@ send_packet(mac_callback_t mac_callback, void *mac_callback_ptr)
 #endif
         len = NETSTACK_RADIO.read(ackbuf, ACK_LEN);
         if(len == ACK_LEN) {
-          leds_on(LEDS_BLUE);
           got_strobe_ack = 1;
           //          encounter_time = last_transmission_time;
           encounter_time = now;
@@ -775,7 +779,6 @@ send_packet(mac_callback_t mac_callback, void *mac_callback_ptr)
   }
 #endif /* WITH_PHASE_OPTIMIZATION */
 
-  leds_off(LEDS_BLUE);
   return ret;
 }
 /*---------------------------------------------------------------------------*/
diff --git a/core/net/mac/phase.c b/core/net/mac/phase.c
index 7368fcd5c..ee355a3ab 100644
--- a/core/net/mac/phase.c
+++ b/core/net/mac/phase.c
@@ -28,7 +28,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: phase.c,v 1.6 2010/03/31 11:54:38 adamdunkels Exp $
+ * $Id: phase.c,v 1.7 2010/03/31 20:27:15 adamdunkels Exp $
  */
 
 /**
@@ -61,7 +61,7 @@ struct phase_queueitem {
 
 MEMB(phase_memb, struct phase_queueitem, PHASE_QUEUESIZE);
 
-#define DEBUG 1
+#define DEBUG 0
 #if DEBUG
 #include <stdio.h>
 #define PRINTF(...) printf(__VA_ARGS__)
@@ -89,7 +89,7 @@ phase_update(const struct phase_list *list,
          phase (rebooted). We try a number of transmissions to it
          before we drop it from the phase list. */
       if(mac_status == MAC_TX_NOACK) {
-        printf("phase noacks %d to %d.%d\n", e->noacks, neighbor->u8[0], neighbor->u8[1]);
+        PRINTF("phase noacks %d to %d.%d\n", e->noacks, neighbor->u8[0], neighbor->u8[1]);
         e->noacks++;
         if(e->noacks >= MAX_NOACKS) {
           list_remove(*list->list, e);
@@ -149,7 +149,7 @@ phase_wait(struct phase_list *list,
     const rimeaddr_t *neighbor = packetbuf_addr(PACKETBUF_ADDR_RECEIVER);
 
     if(rimeaddr_cmp(neighbor, &e->neighbor)) {
-      rtimer_clock_t wait, now, expected;
+      rtimer_clock_t wait, now, expected, additional_wait;
       clock_time_t ctimewait;
       
       /* We expect phases to happen every CYCLE_TIME time
@@ -161,14 +161,21 @@ phase_wait(struct phase_list *list,
 
       /*      printf("neighbor phase 0x%02x (cycle 0x%02x)\n", e->time & (cycle_time - 1),
               cycle_time);*/
+
+      additional_wait = 2 * e->noacks * wait_before;
+
+      /*      if(e->noacks > 0) {
+        printf("additional wait %d\n", additional_wait);
+        }*/
+
       now = RTIMER_NOW();
-      wait = (rtimer_clock_t)((e->time - now - e->noacks * wait_before) &
+      wait = (rtimer_clock_t)((e->time - now) &
                               (cycle_time - 1));
-      if(wait < wait_before) {
+      if(wait < wait_before + additional_wait) {
         wait += cycle_time;
       }
       
-      ctimewait = (CLOCK_SECOND * (wait - wait_before)) / RTIMER_ARCH_SECOND;
+      ctimewait = (CLOCK_SECOND * (wait - wait_before - additional_wait)) / RTIMER_ARCH_SECOND;
 
       if(ctimewait > PHASE_DEFER_THRESHOLD) {
         struct phase_queueitem *p;
@@ -187,7 +194,7 @@ phase_wait(struct phase_list *list,
         }
       }
       
-      expected = now + wait - wait_before;
+      expected = now + wait - wait_before - additional_wait;
       if(!RTIMER_CLOCK_LT(expected, now)) {
         /* Wait until the receiver is expected to be awake */
         while(RTIMER_CLOCK_LT(RTIMER_NOW(), expected)) {