diff --git a/ports/nrf/boards/challenger_840/mpconfigboard.h b/ports/nrf/boards/challenger_840/mpconfigboard.h
index e68fbc76fb..5226c818d4 100644
--- a/ports/nrf/boards/challenger_840/mpconfigboard.h
+++ b/ports/nrf/boards/challenger_840/mpconfigboard.h
@@ -10,6 +10,7 @@
 #define SPI_FLASH_MISO_PIN          (&pin_P0_11)
 #define SPI_FLASH_SCK_PIN           (&pin_P0_14)
 #define SPI_FLASH_CS_PIN            (&pin_P0_08)
+#define SPI_FLASH_MAX_BAUDRATE      20000000
 #endif
 
 #define CIRCUITPY_AUTORELOAD_DELAY_MS 500
diff --git a/supervisor/shared/external_flash/spi_flash.c b/supervisor/shared/external_flash/spi_flash.c
index b47508e051..abff343713 100644
--- a/supervisor/shared/external_flash/spi_flash.c
+++ b/supervisor/shared/external_flash/spi_flash.c
@@ -151,6 +151,7 @@ void spi_flash_init(void) {
     supervisor_flash_spi_bus.base.type = &busio_spi_type;
     common_hal_busio_spi_construct(&supervisor_flash_spi_bus, SPI_FLASH_SCK_PIN, SPI_FLASH_MOSI_PIN, SPI_FLASH_MISO_PIN, false);
     common_hal_busio_spi_never_reset(&supervisor_flash_spi_bus);
+    common_hal_busio_spi_configure(&supervisor_flash_spi_bus, SPI_FLASH_MAX_BAUDRATE, 0, 0, 8);
 
     return;
 }