diff --git a/Makefile b/Makefile
index c33ff195..2bf826f6 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,5 @@
 .SILENT:
+.SECONDARY:
 
 OUTDIR?=build
 REFSDIR?=$(OUTDIR)/refs
@@ -80,12 +81,10 @@ $(OUTDIR)/%.pdf: %.xml $(XMLDEPS) $(TEXMLDEPS)
 		-e 's|\\pageref{#\([^}]*\)}|\\pageref{\1}|g' "$(@:.pdf=.tex)"
 	cd $(OUTDIR); xelatex -interaction=batchmode -no-shell-escape "$(notdir $(basename $@)).tex" && echo "Finished building $@"
 
-.PRECIOUS: $(OUTDIR)/%.js
-$(OUTDIR)/%.js: %.js
+$(OUTDIR)/%.js: %.js $(OUTDIR)
 	cp "$<" "$@"
 
-.PRECIOUS: $(OUTDIR)/%.css
-$(OUTDIR)/%.css: %.css
+$(OUTDIR)/%.css: %.css $(OUTDIR)
 	cp "$<" "$@"
 
 $(EXAMPLESDIR) $(REFSDIR) $(OUTDIR):