diff --git a/hal_st/stm32fxxx/SystemTickTimerService.hpp b/hal_st/stm32fxxx/SystemTickTimerService.hpp
index 5cace662..250b294c 100644
--- a/hal_st/stm32fxxx/SystemTickTimerService.hpp
+++ b/hal_st/stm32fxxx/SystemTickTimerService.hpp
@@ -20,7 +20,7 @@ namespace hal
 
         infra::TimePoint Now() const override;
 
-    private:
+    protected:
         void Invoke() override;
     };
 }