diff --git a/tests/05r1-re-add b/tests/05r1-re-add
index 3da1a4a..fa6bbcb 100644
--- a/tests/05r1-re-add
+++ b/tests/05r1-re-add
@@ -30,6 +30,7 @@ cmp --ignore-initial=$[64*512] --bytes=$[$mdsize0*1024] $dev1 $dev2
 mdadm $md0 -f $dev2; sleep 1
 mdadm $md0 -r $dev2
 if dd if=/dev/zero of=$md0 ; then : ; fi
+blockdev --flushbufs $md0 # ensure writes have been sent.
 mdadm $md0 -a $dev2
 check recovery
 check wait
diff --git a/tests/05r1-re-add-nosuper b/tests/05r1-re-add-nosuper
index 8025a68..058d602 100644
--- a/tests/05r1-re-add-nosuper
+++ b/tests/05r1-re-add-nosuper
@@ -29,6 +29,7 @@ cmp --bytes=$[$mdsize0*1024] $dev1 $dev2
 mdadm $md0 -f $dev2; sleep 1
 mdadm $md0 -r $dev2
 if dd if=/dev/zero of=$md0 ; then : ; fi
+blockdev --flushbufs $md0 # make sure writes have been sent
 mdadm $md0 --re-add $dev2
 check recovery
 check wait