diff --git a/Makefile b/Makefile
index 0d5041e..3664edf 100644
--- a/Makefile
+++ b/Makefile
@@ -99,7 +99,7 @@ disk.rrd:
 		RRA:AVERAGE:0.5:21900:1440
 
 update_disk: disk.rrd
-	rrdtool update $< $(NOW):$(shell sar -F MOUNT --fs=/ 0 -1 |tail -n 1 |awk '{print $$2,$$3}' |tr ' ' ':' )
+	rrdtool update $< $(NOW):$(shell LANG=C sar -F MOUNT --fs=/ 0 -1 |tail -n 1 |awk '{print $$2,$$3}' |tr ' ' ':' )
 
 update: update_cpu update_load update_mem update_net update_disk