diff --git a/package/libubox/libubox.mk b/package/libubox/libubox.mk
index 22efc9acde..b552227ea5 100644
--- a/package/libubox/libubox.mk
+++ b/package/libubox/libubox.mk
@@ -10,12 +10,14 @@ LIBUBOX_LICENSE = LGPLv2.1, GPLv2, BSD-3c, MIT
 LIBUBOX_INSTALL_STAGING = YES
 LIBUBOX_DEPENDENCIES = host-pkgconf $(if $(BR2_PACKAGE_JSON_C),json-c)
 
+ifeq ($(BR2_USE_MMU),y) # fork()
 ifeq ($(BR2_PACKAGE_LUA_5_1),y)
-	LIBUBOX_DEPENDENCIES += lua
-	LIBUBOX_CONF_OPT += -DLUAPATH=$(STAGING_DIR)/usr/lib/lua/5.1 \
-		-DLUA_CFLAGS=-I$(STAGING_DIR)/usr/include
+LIBUBOX_DEPENDENCIES += lua
+LIBUBOX_CONF_OPT += -DLUAPATH=$(STAGING_DIR)/usr/lib/lua/5.1 \
+	-DLUA_CFLAGS=-I$(STAGING_DIR)/usr/include
 else
-	LIBUBOX_CONF_OPT += -DBUILD_LUA:BOOL=OFF
+LIBUBOX_CONF_OPT += -DBUILD_LUA:BOOL=OFF
 endif
+endif # MMU
 
 $(eval $(cmake-package))