diff --git a/Makefile b/Makefile
index 5dbb067..e17bfcf 100644
--- a/Makefile
+++ b/Makefile
@@ -164,6 +164,7 @@ $(BUILD_DIR)/net-daily$(EXTENSION): net.rrd
 $(BUILD_DIR)/disk-daily$(EXTENSION): disk.rrd
 	rrdtool graph $@ --imgformat $(FORMAT) --end now --start end-$(DAY_IN_SECS) \
 		--title "Disque" \
+		--lower-limit 0 \
 		DEF:mbfsfree=$<:mbfsfree:AVERAGE \
 		DEF:mbfsused=$<:mbfsused:AVERAGE \
 		AREA:mbfsused#$(DANGER):mbfsused:STACK \