diff --git a/sbin/ifenslave b/sbin/ifenslave
index 31d3e67..21097aa 100755
--- a/sbin/ifenslave
+++ b/sbin/ifenslave
@@ -93,7 +93,8 @@ for slave in "$@"; do
 	[ -d "/sys/class/net/$slave" ] || error "$slave: no such interface"
 
 	if [ -z "$DETACH" ]; then
-		if [ -h "/sys/class/net/$master/slave_$slave" ]; then
+		if [ -h "/sys/class/net/$master/slave_$slave" ] ||
+		   [ -h "/sys/class/net/$master/lower_$slave" ]; then
 			echo "$slave: already enslaved to $master" >&2
 			continue
 		fi
@@ -107,7 +108,8 @@ for slave in "$@"; do
 		ip link set "$slave" down
 		echo "+$slave" >"/sys/class/net/$master/bonding/slaves" || error "$slave: could not add interface"
 	else
-		if [ ! -h "/sys/class/net/$master/slave_$slave" ]; then
+		if [ ! -h "/sys/class/net/$master/slave_$slave" ] ||
+		   [ ! -h "/sys/class/net/$master/lower_$slave" ]; then
 			echo "$slave: is not enslaved to $master" >&2
 			continue
 		fi