-ARCH ?= $(error Makefile ARCH value not set.)\r
-LUFA_PATH ?= $(error Makefile LUFA_PATH value not set.)\r
+ARCH ?= $(error Makefile ARCH value not set)\r
+LUFA_PATH ?= $(error Makefile LUFA_PATH value not set)\r
+\r
+ifeq ($(ARCH),)\r
+ $(error Makefile ARCH option cannot be blank)\r
+endif\r