--- a/tools/Makefile
+++ b/tools/Makefile
@@ -25,10 +25,10 @@
 $(eval $(call copy_include,$(curdir)))
 
 # prerequisites for the individual targets
-$(curdir)/ := .config
+$(curdir)/ := .config prereq
 $(curdir)//compile = $(1)/prepare
 $(curdir)//install = $(1)/compile
 
-$(eval $(call stampfile,$(curdir),tools))
+$(eval $(call stampfile,$(curdir),tools,install))
 $(eval $(call subdir,$(curdir)))