diff --git a/arch/sandbox/os/Makefile b/arch/sandbox/os/Makefile
index ed92144..b2f9508 100644
--- a/arch/sandbox/os/Makefile
+++ b/arch/sandbox/os/Makefile
@@ -6,9 +6,13 @@
 
 KBUILD_CPPFLAGS += -DCONFIG_MALLOC_SIZE=$(CONFIG_MALLOC_SIZE)
 
-KBUILD_CFLAGS += -Wall
+KBUILD_CFLAGS := -Wall
 NOSTDINC_FLAGS :=
 
+ifeq ($(CONFIG_SANDBOX_LINUX_I386),y)
+KBUILD_CFLAGS += -m32
+endif
+
 obj-y = common.o tap.o
 
 CFLAGS_sdl.o = $(shell pkg-config sdl --cflags)