diff --git a/libraries/AP_HAL_PX4/Scheduler.cpp b/libraries/AP_HAL_PX4/Scheduler.cpp
index 8441b9046b..78b730c7db 100644
--- a/libraries/AP_HAL_PX4/Scheduler.cpp
+++ b/libraries/AP_HAL_PX4/Scheduler.cpp
@@ -443,7 +443,7 @@ void *PX4Scheduler::_uavcan_thread(void *arg)
 }
 #endif
 
-bool PX4Scheduler::in_main_thread()
+bool PX4Scheduler::in_main_thread() const
 {
     return getpid() == _main_task_pid;
 }
diff --git a/libraries/AP_HAL_PX4/Scheduler.h b/libraries/AP_HAL_PX4/Scheduler.h
index 4ca33698c9..46baf58163 100644
--- a/libraries/AP_HAL_PX4/Scheduler.h
+++ b/libraries/AP_HAL_PX4/Scheduler.h
@@ -58,7 +58,7 @@ public:
     void     resume_timer_procs();
     void     reboot(bool hold_in_bootloader);
 
-    bool     in_main_thread();
+    bool     in_main_thread() const override;
     void     system_initialized();
     void     hal_initialized() { _hal_initialized = true; }