diff --git a/cpu/msp430/cc2420-arch-sfd.c b/cpu/msp430/cc2420-arch-sfd.c
index f7535b276..a940b8cab 100644
--- a/cpu/msp430/cc2420-arch-sfd.c
+++ b/cpu/msp430/cc2420-arch-sfd.c
@@ -45,6 +45,7 @@ ISR(TIMERB1, cc2420_timerb1_interrupt)
   ENERGEST_ON(ENERGEST_TYPE_IRQ);
   /* always read TBIV to clear IFG */
   tbiv = TBIV;
+  (void)tbiv;
   if(CC2420_SFD_IS_1) {
     cc2420_sfd_counter++;
     cc2420_sfd_start_time = TBCCR1;
diff --git a/cpu/msp430/cc2520-arch-sfd.c b/cpu/msp430/cc2520-arch-sfd.c
index bafa11b1c..852974b70 100644
--- a/cpu/msp430/cc2520-arch-sfd.c
+++ b/cpu/msp430/cc2520-arch-sfd.c
@@ -44,6 +44,7 @@ ISR(TIMERB1, cc2520_timerb1_interrupt)
   ENERGEST_ON(ENERGEST_TYPE_IRQ);
   /* always read TBIV to clear IFG */
   tbiv = TBIV;
+  (void)tbiv;
   if(CC2520_SFD_IS_1) {
     cc2520_sfd_counter++;
     cc2520_sfd_start_time = TBCCR1;