diff --git a/Makefile b/Makefile
index 0bacc41..95d21f7 100644
--- a/Makefile
+++ b/Makefile
@@ -45,7 +45,11 @@
 	-I..
 
 PKG_CONFIG ?= pkg-config
-BASE_VER ?= 307740
+
+ifeq ($(strip $(BASE_VER)),)
+$(error BASE_VER is not set. Make sure you set it to the correct revision number of libchrome)
+endif
+
 PC_DEPS += libchrome-$(BASE_VER)
 PC_CFLAGS := $(shell $(PKG_CONFIG) --cflags $(PC_DEPS))
 PC_LIBS := $(shell $(PKG_CONFIG) --libs $(PC_DEPS))