diff --git a/tests/10ddf-fail-two-spares b/tests/10ddf-fail-two-spares
index c20eb4a..e00810d 100644
--- a/tests/10ddf-fail-two-spares
+++ b/tests/10ddf-fail-two-spares
@@ -14,8 +14,8 @@ mdadm -CR $member0 -l raid6 -n 4 $dev10 $dev11 $dev12 $dev13 -z 16384
 #	    >/tmp/mdmon.txt 2>&1
 mdadm -CR $member1 -l raid10 -n 4 $dev10 $dev11 $dev12 $dev13 -z 16384
 
-dd if=$sda of=$member0 bs=1M
-dd if=$sda of=$member1 bs=1M skip=16
+dd if=$sda of=$member0 bs=1M count=32
+dd if=$sda of=$member1 bs=1M skip=16 count=16
 
 check wait