diff --git a/package/firewall/Makefile b/package/firewall/Makefile
index 637d0ecccb..57a6e016ab 100644
--- a/package/firewall/Makefile
+++ b/package/firewall/Makefile
@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 PKG_NAME:=firewall
 
 PKG_VERSION:=2
-PKG_RELEASE:=39
+PKG_RELEASE:=40
 
 include $(INCLUDE_DIR)/package.mk
 
diff --git a/package/firewall/files/lib/core_init.sh b/package/firewall/files/lib/core_init.sh
index f2cde1c470..a0b095865e 100644
--- a/package/firewall/files/lib/core_init.sh
+++ b/package/firewall/files/lib/core_init.sh
@@ -247,13 +247,13 @@ fw_load_zone() {
 		for msrc in ${zone_masq_src:-0.0.0.0/0}; do
 			case "$msrc" in
 				*.*) fw_get_negation msrc '-s' "$msrc" ;;
-				*)   fw_get_subnet4 msrc '-s' "$msrc" ;;
+				*)   fw_get_subnet4 msrc '-s' "$msrc" || break ;;
 			esac
 
 			for mdst in ${zone_masq_dest:-0.0.0.0/0}; do
 				case "$mdst" in
 					*.*) fw_get_negation mdst '-d' "$mdst" ;;
-					*)   fw_get_subnet4 mdst '-d' "$mdst" ;;
+					*)   fw_get_subnet4 mdst '-d' "$mdst" || break ;;
 				esac
 
 				fw add $mode n ${chain}_nat MASQUERADE $ { $msrc $mdst }
diff --git a/package/firewall/files/lib/fw.sh b/package/firewall/files/lib/fw.sh
index 7922d222f8..0814ffc315 100644
--- a/package/firewall/files/lib/fw.sh
+++ b/package/firewall/files/lib/fw.sh
@@ -255,9 +255,12 @@ fw_get_subnet4() {
 			[ "${_name#!}" != "$_name" ] && \
 				export -n -- "$_var=! $_flag $_ipaddr/${_netmask:-255.255.255.255}" || \
 				export -n -- "$_var=$_flag $_ipaddr/${_netmask:-255.255.255.255}"
+			return 0
 		;;
-		*) export -n -- "$_var=" ;;
 	esac
+
+	export -n -- "$_var="
+	return 1
 }
 
 fw_check_icmptype4() {