diff --git a/network-scripts/ifup-eth b/network-scripts/ifup-eth
index 134f9759..20c7f572 100755
--- a/network-scripts/ifup-eth
+++ b/network-scripts/ifup-eth
@@ -295,7 +295,7 @@ else
                 if [ "${REALDEVICE}" != "lo" ] && ! is_false "${arpcheck[$idx]}"; then
                     for (( tries=0; tries<${ARPING_TRIES:=1}; tries++ )); do
                         ARPING=$(/sbin/arping -c 2 -w ${ARPING_WAIT:-3} -D -I ${REALDEVICE} ${ipaddr[$idx]})
-                        [ $? = 0 ] && break
+                        [ "$?" -eq 0 ] && break
                         ARPINGMAC=$(echo $ARPING |  sed -ne 's/.*\[\(.*\)\].*/\1/p')
                         if [ -n "${ARPINGMAC}" ]; then
                             net_log $"Error, some other host ($ARPINGMAC) already uses address ${ipaddr[$idx]}."