Use CONFIG after defining it. Define CONFIG before using it.
	Change on 2015/01/06 by yangg <yangg@google.com>
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=83383325
diff --git a/Makefile b/Makefile
index 76fa9e1..49b0bd6 100644
--- a/Makefile
+++ b/Makefile
@@ -49,16 +49,13 @@
 LDFLAGS_msan = -fsanitize=memory
 DEFINES_msan = NDEBUG
 
-ifndef VALID_CONFIG_$(CONFIG)
-$(error Invalid CONFIG value '$(CONFIG)')
-endif
-
 # General settings.
 # You may want to change these depending on your system.
 
 prefix ?= /usr/local
 
 PROTOC = protoc
+CONFIG ?= opt
 CC = $(CC_$(CONFIG))
 CXX = $(CXX_$(CONFIG))
 LD = $(LD_$(CONFIG))
@@ -68,13 +65,15 @@
 INSTALL = install -D
 RM = rm -f
 
+ifndef VALID_CONFIG_$(CONFIG)
+$(error Invalid CONFIG value '$(CONFIG)')
+endif
+
 HOST_CC = $(CC)
 HOST_CXX = $(CXX)
 HOST_LD = $(LD)
 HOST_LDXX = $(LDXX)
 
-CONFIG ?= opt
-
 CPPFLAGS += $(CPPFLAGS_$(CONFIG))
 DEFINES += $(DEFINES_$(CONFIG))
 LDFLAGS += $(LDFLAGS_$(CONFIG))