diff --git a/Makefile b/Makefile
index b85d8bf369a8cb2e7a949e72f1304bbf1729b42d..0f5f9c854955a3c469ba69025509abd05ece1b01 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,11 @@
 QFILES != find . -name '[ws]s[[:digit:]][[:digit:]].q' -type f
 
-sp.json: sp.q
-	./gen.pl $< > $@
+.PHONY: all
+all: sp.json
 
-sp.q: $(QFILES)
-	cat $^ > $@
+sp.json: $(QFILES)
+	./gen.pl $^ > $@
+
+.PHONY: clean
+clean:
+	rm -f sp.json