diff --git a/Tools/AP_Bootloader/bl_protocol.cpp b/Tools/AP_Bootloader/bl_protocol.cpp
index c0b7171a20..c4577cd231 100644
--- a/Tools/AP_Bootloader/bl_protocol.cpp
+++ b/Tools/AP_Bootloader/bl_protocol.cpp
@@ -163,7 +163,7 @@ extern AP_FlashIface_JEDEC ext_flash;
 /*
   1ms timer tick callback
  */
-static void sys_tick_handler(void *ctx)
+static void sys_tick_handler(virtual_timer_t* vt, void *ctx)
 {
     chSysLockFromISR();
     chVTSetI(&systick_vt, chTimeMS2I(1), sys_tick_handler, nullptr);