diff --git a/libraries/AP_Radio/driver_cc2500.h b/libraries/AP_Radio/driver_cc2500.h
index 702ee7e40a..2038bb2733 100644
--- a/libraries/AP_Radio/driver_cc2500.h
+++ b/libraries/AP_Radio/driver_cc2500.h
@@ -155,7 +155,7 @@ public:
     bool Reset(void);
 
     bool lock_bus(void) {
-        return dev->get_semaphore()->take(HAL_SEMAPHORE_BLOCK_FOREVER);
+        return dev && dev->get_semaphore()->take(HAL_SEMAPHORE_BLOCK_FOREVER);
     }
     void unlock_bus(void) {
         dev->get_semaphore()->give();