test: read from the right device

diff --git a/test/units/testsuite-17.10.sh b/test/units/testsuite-17.10.sh
index f970831..20f120a 100755 (executable)
--- a/test/units/testsuite-17.10.sh
+++ b/test/units/testsuite-17.10.sh
@@ -25,7 +25,7 @@ netdev=dummy17.10
 ip link add $netdev type dummy
 
 blk="$(mktemp)"
-dd if=/dev/null of="$blk" bs=1M count=1
+dd if=/dev/zero of="$blk" bs=1M count=1
 loopdev="$(losetup --show -f "$blk")"
 
 udevadm -h