diff --git a/src/nat_porttrigger.c b/src/nat_porttrigger.c
index b74d45658f5d951548f9889cc749fdb1a27cd7d0..cd2200b08ae781f29a018e15c9c670b165032680 100644
--- a/src/nat_porttrigger.c
+++ b/src/nat_porttrigger.c
@@ -385,6 +385,8 @@ static int get_NATPortTrigger_Protocol(char *refparam, struct dmctx *ctx, void *
 
 static int set_NATPortTrigger_Protocol(char *refparam, struct dmctx *ctx, void *data, char *instance, char *value, int action)
 {
+	char *NATProtocol[] = {"TCP", "UDP", NULL};
+
 	switch (action)	{
 		case VALUECHECK:
 			if (bbfdm_validate_string(ctx, value, -1, -1, NATProtocol, NULL))
@@ -467,6 +469,8 @@ static int get_NATPortTriggerRule_Protocol(char *refparam, struct dmctx *ctx, vo
 
 static int set_NATPortTriggerRule_Protocol(char *refparam, struct dmctx *ctx, void *data, char *instance, char *value, int action)
 {
+	char *NATProtocol[] = {"TCP", "UDP", NULL};
+
 	switch (action)	{
 		case VALUECHECK:
 			if (bbfdm_validate_string(ctx, value, -1, -1, NATProtocol, NULL))