diff --git a/test b/test
index 2ceea46..3acb6c1 100644
--- a/test
+++ b/test
@@ -170,6 +170,11 @@ testdev() {
    dsize=$[dvsize/chunk]
    dsize=$[dsize*chunk]
    rasize=$[dsize*2*cnt]
+   # rasize is in sectors
+   if [ -n "$DEV_ROUND_K" ]; then
+      rasize=$[rasize/DEV_ROUND_K/2]
+      rasize=$[rasize*DEV_ROUND_K*2]
+   fi
    if [ `/sbin/blockdev --getsize $dev` -eq 0 ]; then sleep 2 ; fi
    if [ $rasize -ne `/sbin/blockdev --getsize $dev` ]
    then
diff --git a/tests/09imsm-create-fail-rebuild b/tests/09imsm-create-fail-rebuild
index 8069576..68fdd09 100644
--- a/tests/09imsm-create-fail-rebuild
+++ b/tests/09imsm-create-fail-rebuild
@@ -1,5 +1,8 @@
 # sanity check array creation
 
+# IMSM rounds to multiples of one mebibyte - 1024K
+DEV_ROUND_K=1024
+
 num_disks=2
 mdadm -CR $container -e imsm -n $num_disks $dev0 $dev1
 imsm_check container $num_disks