diff --git a/Makefile b/Makefile
index 99e2310..412f224 100644
--- a/Makefile
+++ b/Makefile
@@ -239,7 +239,8 @@ endif
 
 CFLAGS =
 ifeq ($(ENABLE_CLANG),0)
-	CFLAGS += -Os -Wall -Werror -mcpu=cortex-m0 -fno-builtin -fshort-enums -fno-delete-null-pointer-checks -std=c2x -MMD
+	CFLAGS += -Oz -Wall -Werror -mcpu=cortex-m0 -fshort-enums -fno-delete-null-pointer-checks -std=c2x -MMD
+	#CFLAGS += -Os -Wall -Werror -mcpu=cortex-m0 -fno-builtin -fshort-enums -fno-delete-null-pointer-checks -std=c2x -MMD
 	#CFLAGS += -Os -Wall -Werror -mcpu=cortex-m0 -fno-builtin -fshort-enums -fno-delete-null-pointer-checks -std=c11 -MMD
 	#CFLAGS += -Os -Wall -Werror -mcpu=cortex-m0 -fno-builtin -fshort-enums -fno-delete-null-pointer-checks -std=c99 -MMD
 	#CFLAGS += -Os -Wall -Werror -mcpu=cortex-m0 -fno-builtin -fshort-enums -fno-delete-null-pointer-checks -std=gnu99 -MMD