diff --git a/plugins/disk/linux_diskstat_ b/plugins/disk/linux_diskstat_
index de522d38..6628307b 100755
--- a/plugins/disk/linux_diskstat_
+++ b/plugins/disk/linux_diskstat_
@@ -498,7 +498,7 @@ sub read_sysfs {
         $cur_device =~ tr#!#/#;
 
         # Faking missing diskstats values
-        unshift @elems, ( '', '', $cur_device );
+        unshift @elems, ( -1, -1, $cur_device );
 
         push @lines, \@elems;