diff --git a/ports/stm/boards/espruino_pico/mpconfigboard.mk b/ports/stm/boards/espruino_pico/mpconfigboard.mk
index b1b023dd58..556ff35c45 100644
--- a/ports/stm/boards/espruino_pico/mpconfigboard.mk
+++ b/ports/stm/boards/espruino_pico/mpconfigboard.mk
@@ -9,6 +9,8 @@ MCU_SERIES = F4
 MCU_VARIANT = STM32F401xE
 MCU_PACKAGE = UFQFPN48
 
+OPTIMIZATION_FLAGS = -Os
+
 LD_COMMON = boards/common_default.ld
 # use for internal flash
 LD_FILE = boards/STM32F401xd_fs.ld