diff --git a/ports/stm/boards/meowbit_v121/mpconfigboard.mk b/ports/stm/boards/meowbit_v121/mpconfigboard.mk
index c416700e3c..86b0cb5ab4 100644
--- a/ports/stm/boards/meowbit_v121/mpconfigboard.mk
+++ b/ports/stm/boards/meowbit_v121/mpconfigboard.mk
@@ -20,3 +20,5 @@ LD_COMMON = boards/common_default.ld
 LD_FILE = boards/STM32F401xe_boot.ld
 # For debugging - also comment BOOTLOADER_OFFSET and BOARD_VTOR_DEFER
 # LD_FILE = boards/STM32F401xe_fs.ld
+
+CIRCUITPY_ULAB = 0
diff --git a/ports/stm/boards/thunderpack/mpconfigboard.mk b/ports/stm/boards/thunderpack/mpconfigboard.mk
index d303582e0e..8f645068d7 100644
--- a/ports/stm/boards/thunderpack/mpconfigboard.mk
+++ b/ports/stm/boards/thunderpack/mpconfigboard.mk
@@ -15,3 +15,5 @@ MCU_PACKAGE = UFQFPN48
 
 LD_COMMON = boards/common_nvm.ld
 LD_FILE = boards/STM32F411_nvm.ld
+
+CIRCUITPY_ULAB = 0