diff --git a/Makefile b/Makefile
index f55f728..e860ce7 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,7 @@
 all: ucloud-networking.png ucloud-vm-states.png
 
+clean:
+	rm -f *.png
+
 %.png: %.dot
-	echo dot -Tpng < $< > $@
+	dot -Tpng < $< > $@
diff --git a/ucloud-ipv6-networks.dot b/ucloud-networking.dot
similarity index 100%
rename from ucloud-ipv6-networks.dot
rename to ucloud-networking.dot