diff --git a/ini/stm32f4.ini b/ini/stm32f4.ini
index c8f8676b68..7ff0443df6 100644
--- a/ini/stm32f4.ini
+++ b/ini/stm32f4.ini
@@ -422,7 +422,7 @@ board_build.offset          = 0xC000
 board_upload.offset_address = 0x0800C000
 board_build.rename          = mks_monster8.bin
 build_flags                 = ${stm32_variant.build_flags} ${stm32f4_I2C1_CAN.build_flags}
-                              -DHAL_PCD_MODULE_ENABLED
+                              -DHAL_PCD_MODULE_ENABLED -DTIMER_SERIAL=TIM4
 debug_tool                  = jlink
 upload_protocol             = jlink