diff --git a/libraries/AP_HAL_ChibiOS/RCInput.cpp b/libraries/AP_HAL_ChibiOS/RCInput.cpp
index 6ea3436d9c..8eebf702ed 100644
--- a/libraries/AP_HAL_ChibiOS/RCInput.cpp
+++ b/libraries/AP_HAL_ChibiOS/RCInput.cpp
@@ -176,11 +176,15 @@ void RCInput::_timer_tick(void)
     }
 #endif
 
+#if HAL_WITH_IO_MCU
     uint32_t now = AP_HAL::millis();
     const bool have_iocmu_rc = (_rcin_last_iomcu_ms != 0 && now - _rcin_last_iomcu_ms < 400);
     if (!have_iocmu_rc) {
         _rcin_last_iomcu_ms = 0;
     }
+#else
+    const bool have_iocmu_rc = false;
+#endif
 
     if (rcprot.new_input() && !have_iocmu_rc) {
         WITH_SEMAPHORE(rcin_mutex);
diff --git a/libraries/AP_HAL_ChibiOS/RCInput.h b/libraries/AP_HAL_ChibiOS/RCInput.h
index 08ba46d58c..0b3ec8ea5a 100644
--- a/libraries/AP_HAL_ChibiOS/RCInput.h
+++ b/libraries/AP_HAL_ChibiOS/RCInput.h
@@ -69,7 +69,9 @@ private:
     int16_t _rssi = -1;
     int16_t _rx_link_quality = -1;
     uint32_t _rcin_timestamp_last_signal;
+#if HAL_WITH_IO_MCU
     uint32_t _rcin_last_iomcu_ms;
+#endif
     bool _init;
     const char *last_protocol;