diff --git a/make/projects-dir.mk b/make/projects-dir.mk
index 173f9d26..10de5e13 100644
--- a/make/projects-dir.mk
+++ b/make/projects-dir.mk
@@ -15,6 +15,9 @@ all:
 clean:
 	por p in $(PROJECTS); do make -C $$p clean || break; done
 
+clean-dirs:
+	ls */dirs-all.done 2>/dev/null | sed 's%/.*%%' | xargs -r build.py -b $(shell pwd) clean
+
 cpp:
 	@find $(PROJECTS) -name '*.cpp' | grep /worker/ | grep -ve "old\|tmp\|nomake\|new" | \
 		while read f; do d=`dirname $$f`; if [ $$d/generate_code.sh ]; then echo $$f; fi ;\