--- old/common/makefiles/MakeBase.gmk	2012-07-03 20:04:07.767902146 +0200
+++ new/common/makefiles/MakeBase.gmk	2012-07-03 20:04:07.657900518 +0200
@@ -138,6 +138,7 @@
 
 # Hook to be called as the very first thing when running a normal build
 define AtRootMakeStart
+	$(if $(findstring -j,$(MAKEFLAGS)), $(error make -j is not supported, use make JOBS=n))
 	$(call PrintStartMessage)
 	$(call StartTimer)
 endef