diff --git a/net/mwan3/files/lib/mwan3/mwan3.sh b/net/mwan3/files/lib/mwan3/mwan3.sh
index 3c4f25cc4..6c8e50080 100644
--- a/net/mwan3/files/lib/mwan3/mwan3.sh
+++ b/net/mwan3/files/lib/mwan3/mwan3.sh
@@ -1067,7 +1067,7 @@ mwan3_report_iface_status()
 		IPT="$IPT6"
 	fi
 
-	if [ -z "$id" -o -z "$device" ]; then
+	if [ -z "$id" ] || [ -z "$device" ]; then
 		result="offline"
 	elif [ -n "$($IP rule | awk '$1 == "'$(($id+1000)):'"')" ] && \
 		[ -n "$($IP rule | awk '$1 == "'$(($id+2000)):'"')" ] && \