diff --git a/nuttx/configs/px4fmu/common/Make.defs b/nuttx/configs/px4fmu/common/Make.defs
index 00a489eabf..7ba4e694a1 100644
--- a/nuttx/configs/px4fmu/common/Make.defs
+++ b/nuttx/configs/px4fmu/common/Make.defs
@@ -55,7 +55,7 @@ NM			 = $(CROSSDEV)nm
 OBJCOPY			 = $(CROSSDEV)objcopy
 OBJDUMP			 = $(CROSSDEV)objdump
 
-MAXOPTIMIZATION		 = -O3
+MAXOPTIMIZATION		 = -Os
 ARCHCPUFLAGS		 = -mcpu=cortex-m4 \
 			   -mthumb \
 			   -march=armv7e-m \