diff --git a/ports/nrf/mpconfigport.h b/ports/nrf/mpconfigport.h
index 464a0b3bd5..5fdc0f0198 100644
--- a/ports/nrf/mpconfigport.h
+++ b/ports/nrf/mpconfigport.h
@@ -141,7 +141,7 @@
 #define CIRCUITPY_BLE_CONFIG_START_ADDR (CIRCUITPY_INTERNAL_NVM_START_ADDR - CIRCUITPY_BLE_CONFIG_SIZE)
 
 // The firmware space is the space left over between the fixed lower and upper regions.
-#define CIRCUITPY_FIRMWARE_SIZE (CIRCUITPY_INTERNAL_FLASH_FILESYSTEM_START_ADDR - CIRCUITPY_FIRMWARE_START_ADDR)
+#define CIRCUITPY_FIRMWARE_SIZE (CIRCUITPY_INTERNAL_FLASH_FILESYSTEM_START_ADDR - CIRCUITPY_FIRMWARE_START_ADDR - CIRCUITPY_BLE_CONFIG_SIZE)
 
 #if BOOTLOADER_START_ADDR % FLASH_ERASE_SIZE != 0
 #error BOOTLOADER_START_ADDR must be on a flash erase boundary.