diff --git a/libraries/GCS_MAVLink/GCS.h b/libraries/GCS_MAVLink/GCS.h
index dfab6165d1..e7e1943b1e 100644
--- a/libraries/GCS_MAVLink/GCS.h
+++ b/libraries/GCS_MAVLink/GCS.h
@@ -578,6 +578,11 @@ protected:
     void handle_set_gps_global_origin(const mavlink_message_t &msg);
     void handle_setup_signing(const mavlink_message_t &msg) const;
     virtual MAV_RESULT handle_preflight_reboot(const mavlink_command_long_t &packet, const mavlink_message_t &msg);
+    struct {
+        HAL_Semaphore sem;
+        bool taken;
+    } _deadlock_sem;
+    void deadlock_sem(void);
 
     // reset a message interval via mavlink:
     MAV_RESULT handle_command_set_message_interval(const mavlink_command_long_t &packet);
diff --git a/libraries/GCS_MAVLink/GCS_Common.cpp b/libraries/GCS_MAVLink/GCS_Common.cpp
index 781d8e5a0d..a46dcaed10 100644
--- a/libraries/GCS_MAVLink/GCS_Common.cpp
+++ b/libraries/GCS_MAVLink/GCS_Common.cpp
@@ -3162,6 +3162,16 @@ MAV_RESULT GCS_MAVLINK::handle_preflight_reboot(const mavlink_command_long_t &pa
 #endif
         }
 #endif
+        if (is_equal(packet.param4, 100.0f)) {
+            send_text(MAV_SEVERITY_WARNING,"Creating mutex deadlock");
+            hal.scheduler->register_io_process(FUNCTOR_BIND_MEMBER(&GCS_MAVLINK::deadlock_sem, void));
+            while (!_deadlock_sem.taken) {
+                hal.scheduler->delay(1);
+            }
+            WITH_SEMAPHORE(_deadlock_sem.sem);
+            send_text(MAV_SEVERITY_WARNING,"deadlock passed");
+            return MAV_RESULT_ACCEPTED;
+        }
     }
 
     // refuse reboot when armed:
@@ -3205,6 +3215,17 @@ MAV_RESULT GCS_MAVLINK::handle_preflight_reboot(const mavlink_command_long_t &pa
     return MAV_RESULT_FAILED;
 }
 
+/*
+  take a semaphore and do not release it, triggering a deadlock
+ */
+void GCS_MAVLINK::deadlock_sem(void)
+{
+    if (!_deadlock_sem.taken) {
+        _deadlock_sem.taken = true;
+        _deadlock_sem.sem.take_blocking();
+    }
+}
+
 /*
   handle a flight termination request
  */