diff --git a/cpu/avr/radio/rf230bb/halbb.c b/cpu/avr/radio/rf230bb/halbb.c
index 53deb1c8a..6aa991eb6 100644
--- a/cpu/avr/radio/rf230bb/halbb.c
+++ b/cpu/avr/radio/rf230bb/halbb.c
@@ -700,10 +700,12 @@ ISR(TRX24_TX_END_vect)
   rf230_txendwait=0;
 }
 
+extern volatile uint8_t rf230_pending;
 /* Frame address has matched ours */
 ISR(TRX24_XAH_AMI_vect)
 {
 //	DEBUGFLOW('8');
+        rf230_pending=1;
 }
 
 /* CCAED measurement has completed */
diff --git a/platform/osd-merkur/contiki-conf.h b/platform/osd-merkur/contiki-conf.h
index 2867cbc61..95f61808a 100644
--- a/platform/osd-merkur/contiki-conf.h
+++ b/platform/osd-merkur/contiki-conf.h
@@ -238,7 +238,7 @@ typedef unsigned short uip_stats_t;
 #define NETSTACK_CONF_MAC         csma_driver
 #define NETSTACK_CONF_RDC         contikimac_driver
 /* Default is two CCA separated by 500 usec */
-#define NETSTACK_CONF_RDC_CHANNEL_CHECK_RATE   16
+#define NETSTACK_CONF_RDC_CHANNEL_CHECK_RATE   8
 /* Wireshark won't decode with the header, but padded packets will fail ipv6 checksum */
 #define CONTIKIMAC_CONF_WITH_CONTIKIMAC_HEADER 0
 /* So without the header this needed for RPL mesh to form */