diff --git a/management/univention-join/univention-server-join b/management/univention-join/univention-server-join
index 2ac2ca0dcd..22e3f37f81 100755
--- a/management/univention-join/univention-server-join
+++ b/management/univention-join/univention-server-join
@@ -131,8 +131,7 @@ do
 			shift 2 || exit 2
 			;;
 		"-mac")
-			MAC+="${2:?missing ethernet MAC address}
-"
+			MAC+=("${2:?missing ethernet MAC address}")
 			shift 2 || exit 2
 			;;
 		"-bindaccount")
@@ -316,9 +315,9 @@ create_entry () {
 			fi
 		fi
 		if [ -n "$MAC" ]; then
-			while read line; do
-				args+=(--set mac="$line")
-			done <<< "$MAC"
+			for i in "${MAC[@]}"; do
+				args+=(--set mac="$i")
+			done
 		fi
 		# DHCP
 		case "$module" in