diff --git a/libraries/AP_IOMCU/AP_IOMCU.cpp b/libraries/AP_IOMCU/AP_IOMCU.cpp
index c4707f6624..6f498534d5 100644
--- a/libraries/AP_IOMCU/AP_IOMCU.cpp
+++ b/libraries/AP_IOMCU/AP_IOMCU.cpp
@@ -157,6 +157,7 @@ void AP_IOMCU::event_failed(uint8_t event)
 void AP_IOMCU::thread_main(void)
 {
     thread_ctx = chThdGetSelfX();
+    chEvtSignal(thread_ctx, initial_event_mask);
 
     uart.begin(1500*1000, 256, 256);
     uart.set_blocking_writes(false);
@@ -543,6 +544,9 @@ void AP_IOMCU::trigger_event(uint8_t event)
 {
     if (thread_ctx != nullptr) {
         chEvtSignal(thread_ctx, EVENT_MASK(event));
+    } else {
+        // thread isn't started yet, trigger this event once it is started
+        initial_event_mask |= EVENT_MASK(event);
     }
 }
 
diff --git a/libraries/AP_IOMCU/AP_IOMCU.h b/libraries/AP_IOMCU/AP_IOMCU.h
index 7aca6ead52..911bf0cad8 100644
--- a/libraries/AP_IOMCU/AP_IOMCU.h
+++ b/libraries/AP_IOMCU/AP_IOMCU.h
@@ -112,6 +112,8 @@ private:
     // IOMCU thread
     thread_t *thread_ctx;
 
+    eventmask_t initial_event_mask;
+
     // time when we last read various pages
     uint32_t last_status_read_ms;
     uint32_t last_rc_read_ms;