diff --git a/ports/stm32/Makefile b/ports/stm32/Makefile
index b43f284b1a..c0bf4be32e 100644
--- a/ports/stm32/Makefile
+++ b/ports/stm32/Makefile
@@ -72,7 +72,7 @@ PYDFU ?= $(TOP)/tools/pydfu.py
 DFU_UTIL ?= dfu-util
 BOOTLOADER_DFU_USB_VID ?= 0x0483
 BOOTLOADER_DFU_USB_PID ?= 0xDF11
-STFLASH ?= st-flash
+STFLASH ?= st-flash --connect-under-reset
 OPENOCD ?= openocd
 OPENOCD_CONFIG ?= boards/openocd_stm32f4.cfg
 
diff --git a/ports/stm32/boards/NUCLEO_H723ZG/mpconfigboard.mk b/ports/stm32/boards/NUCLEO_H723ZG/mpconfigboard.mk
index 56f30c42bd..fcb235c868 100644
--- a/ports/stm32/boards/NUCLEO_H723ZG/mpconfigboard.mk
+++ b/ports/stm32/boards/NUCLEO_H723ZG/mpconfigboard.mk
@@ -26,5 +26,4 @@ MICROPY_HW_ENABLE_ISR_UART_FLASH_FUNCS_IN_RAM = 1
 FROZEN_MANIFEST ?= $(BOARD_DIR)/manifest.py
 
 # Flash tool configuration
-STFLASH = st-flash --connect-under-reset
 OPENOCD_CONFIG = boards/openocd_stm32h7_dual_bank.cfg
diff --git a/ports/stm32/boards/NUCLEO_H743ZI/mpconfigboard.mk b/ports/stm32/boards/NUCLEO_H743ZI/mpconfigboard.mk
index da991c5879..0f528939c9 100644
--- a/ports/stm32/boards/NUCLEO_H743ZI/mpconfigboard.mk
+++ b/ports/stm32/boards/NUCLEO_H743ZI/mpconfigboard.mk
@@ -26,5 +26,4 @@ MICROPY_HW_ENABLE_ISR_UART_FLASH_FUNCS_IN_RAM = 1
 FROZEN_MANIFEST ?= $(BOARD_DIR)/manifest.py
 
 # Flash tool configuration
-STFLASH = st-flash --connect-under-reset
 OPENOCD_CONFIG = boards/openocd_stm32h7_dual_bank.cfg
diff --git a/ports/stm32/mboot/Makefile b/ports/stm32/mboot/Makefile
index 7226dd353f..c049017734 100755
--- a/ports/stm32/mboot/Makefile
+++ b/ports/stm32/mboot/Makefile
@@ -54,7 +54,7 @@ DFU=$(TOP)/tools/dfu.py
 PYDFU ?= $(TOP)/tools/pydfu.py
 BOOTLOADER_DFU_USB_VID ?= 0x0483
 BOOTLOADER_DFU_USB_PID ?= 0xDF11
-STFLASH ?= st-flash
+STFLASH ?= st-flash --connect-under-reset
 OPENOCD ?= openocd
 OPENOCD_CONFIG ?= boards/openocd_stm32f4.cfg