diff --git a/cpu/msp430/cc2420-arch-sfd.c b/cpu/msp430/cc2420-arch-sfd.c
index 023130baa..69ae6510d 100644
--- a/cpu/msp430/cc2420-arch-sfd.c
+++ b/cpu/msp430/cc2420-arch-sfd.c
@@ -26,7 +26,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * @(#)$Id: cc2420-arch-sfd.c,v 1.2 2010/01/19 13:11:01 adamdunkels Exp $
+ * @(#)$Id: cc2420-arch-sfd.c,v 1.3 2010/01/26 10:20:16 adamdunkels Exp $
  */
 
 #include <io.h>
@@ -35,9 +35,9 @@
 #include "dev/spi.h"
 #include "dev/cc2420.h"
 
-uint8_t cc2420_arch_sfd_counter;
-uint16_t cc2420_arch_sfd_start_time;
-uint16_t cc2420_arch_sfd_end_time;
+volatile uint8_t cc2420_arch_sfd_counter;
+volatile uint16_t cc2420_arch_sfd_start_time;
+volatile uint16_t cc2420_arch_sfd_end_time;
 
 /*---------------------------------------------------------------------------*/
 /* SFD interrupt for timestamping radio packets */
diff --git a/cpu/msp430/cc2420-arch-sfd.h b/cpu/msp430/cc2420-arch-sfd.h
index d11038dfc..2574509bd 100644
--- a/cpu/msp430/cc2420-arch-sfd.h
+++ b/cpu/msp430/cc2420-arch-sfd.h
@@ -26,14 +26,14 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * @(#)$Id: cc2420-arch-sfd.h,v 1.2 2010/01/19 13:11:01 adamdunkels Exp $
+ * @(#)$Id: cc2420-arch-sfd.h,v 1.3 2010/01/26 10:20:16 adamdunkels Exp $
  */
 #ifndef CC2420_ARCH_SFD_H
 #define CC2420_ARCH_SFD_H
 
-extern uint8_t cc2420_arch_sfd_counter;
-extern uint16_t cc2420_arch_sfd_start_time;
-extern uint16_t cc2420_arch_sfd_end_time;
+extern volatile uint8_t cc2420_arch_sfd_counter;
+extern volatile uint16_t cc2420_arch_sfd_start_time;
+extern volatile uint16_t cc2420_arch_sfd_end_time;
 
 void cc2420_arch_sfd_init(void);