diff --git a/Makefile b/Makefile
index 04a7db007..cfe2aa752 100644
--- a/Makefile
+++ b/Makefile
@@ -25,11 +25,12 @@ node_modules: .npmrc package.json
 .PHONY: clean
 clean:
 	rm -rf node_modules
+	rm -rf .stack-work .stack-work-build .stack-work-run .stack-work-test .stack-work-doc
 
 .PHONY: %.lock
 %.lock:
 	[ -e $@ ] || touch $@
-	flock -en $@ :
+	flock -en $@ true
 
 .develop.env:
 	(in-develop | grep -q 'In develop') || (echo "Not in develop!" 2>&1; exit 1)
@@ -40,12 +41,13 @@ clean:
 
 .PHONY: --stack-work-%
 --stack-work-%: .stack-work.lock
-	[[ -e .stack-work && -e .stack-work-$* ]] && (echo ".stack-work collides with .stack-work-$*, please resolve manually" 1>&2; exit 1)
-	[[ -e .stack-work && ! -e .stack-work-$* ]] || mv .stack-work-$* .stack-work
+	[[ -d .stack-work && -d .stack-work-$* ]] && (echo ".stack-work collides with .stack-work-$*, please resolve manually" 1>&2; exit 1) || :
+	[[ ! -d .stack-work-$* ]] || mv .stack-work-$* .stack-work
 
 .PHONY: --stack-krow-%
 --stack-krow-%:
-	[[ -e .stack-work-$* && echo ".stack-work-$* already exists, please resolve manually" 1>&2; exit 1 ]] || mv .stack-work .stack-work-$*
+	[[ -d .stack-work-$* && echo ".stack-work-$* already exists, please resolve manually" 1>&2; exit 1 ]]
+	mv .stack-work .stack-work-$*
 	flock -u .stack-work.lock
 
 # TODO: yarn2nix target