diff --git a/ports/stm32/main.c b/ports/stm32/main.c
index 62cba54345..42bebf079d 100644
--- a/ports/stm32/main.c
+++ b/ports/stm32/main.c
@@ -268,7 +268,7 @@ MP_NOINLINE STATIC bool init_flash_fs(uint reset_mode) {
 }
 #endif
 
-#if MICROPY_HW_HAS_SDCARD
+#if MICROPY_HW_SDCARD_MOUNT_AT_BOOT
 STATIC bool init_sdcard_fs(void) {
     bool first_part = true;
     for (int part_num = 1; part_num <= 4; ++part_num) {
@@ -620,7 +620,7 @@ soft_reset:
     #endif
 
     bool mounted_sdcard = false;
-    #if MICROPY_HW_HAS_SDCARD
+    #if MICROPY_HW_SDCARD_MOUNT_AT_BOOT
     // if an SD card is present then mount it on /sd/
     if (sdcard_is_present()) {
         // if there is a file in the flash called "SKIPSD", then we don't mount the SD card
diff --git a/ports/stm32/mpconfigboard_common.h b/ports/stm32/mpconfigboard_common.h
index 2acdcc2f72..d4e7c20145 100644
--- a/ports/stm32/mpconfigboard_common.h
+++ b/ports/stm32/mpconfigboard_common.h
@@ -97,6 +97,11 @@
 #define MICROPY_HW_HAS_SDCARD (0)
 #endif
 
+// Whether to automatically mount (and boot from) the SD card if it's present
+#ifndef MICROPY_HW_SDCARD_MOUNT_AT_BOOT
+#define MICROPY_HW_SDCARD_MOUNT_AT_BOOT (MICROPY_HW_HAS_SDCARD)
+#endif
+
 // Whether to enable the MMA7660 driver, exposed as pyb.Accel
 #ifndef MICROPY_HW_HAS_MMA7660
 #define MICROPY_HW_HAS_MMA7660 (0)