diff --git a/conf.c b/conf.c
index a79beb5..ad2a093 100644
--- a/conf.c
+++ b/conf.c
@@ -1675,6 +1675,7 @@ void conf(struct ctx *c, int argc, char **argv)
 		c->no_map_gw = 1;
 
 	/* Inbound port options can be parsed now (after IPv4/IPv6 settings) */
+	udp_portmap_clear();
 	optind = 1;
 	do {
 		name = getopt_long(argc, argv, optstring, options, NULL);
diff --git a/udp.c b/udp.c
index e479f92..1b7650d 100644
--- a/udp.c
+++ b/udp.c
@@ -238,6 +238,20 @@ static struct sockaddr_in6 udp6_localname = {
 static struct mmsghdr	udp4_mh_splice		[UDP_MAX_FRAMES];
 static struct mmsghdr	udp6_mh_splice		[UDP_MAX_FRAMES];
 
+/**
+ * udp_portmap_clear() - Clear UDP port map before configuration
+ */
+void udp_portmap_clear(void)
+{
+	unsigned i;
+
+	for (i = 0; i < NUM_PORTS; i++) {
+		udp_tap_map[V4][i].sock = udp_tap_map[V6][i].sock = -1;
+		udp_splice_ns[V4][i].sock = udp_splice_ns[V6][i].sock = -1;
+		udp_splice_init[V4][i].sock = udp_splice_init[V6][i].sock = -1;
+	}
+}
+
 /**
  * udp_invert_portmap() - Compute reverse port translations for return packets
  * @fwd:	Port forwarding configuration to compute reverse map for
@@ -522,7 +536,7 @@ static void udp_splice_sendfrom(const struct ctx *c, unsigned start, unsigned n,
 	if (from_pif == PIF_SPLICE) {
 		src += c->udp.fwd_in.rdelta[src];
 		s = udp_splice_init[v6][src].sock;
-		if (!s && allow_new)
+		if (s < 0 && allow_new)
 			s = udp_splice_new(c, v6, src, false);
 
 		if (s < 0)
@@ -534,7 +548,7 @@ static void udp_splice_sendfrom(const struct ctx *c, unsigned start, unsigned n,
 		ASSERT(from_pif == PIF_HOST);
 		src += c->udp.fwd_out.rdelta[src];
 		s = udp_splice_ns[v6][src].sock;
-		if (!s && allow_new) {
+		if (s < 0 && allow_new) {
 			struct udp_splice_new_ns_arg arg = {
 				c, v6, src, -1,
 			};
@@ -849,7 +863,9 @@ int udp_tap_handler(struct ctx *c, uint8_t pif,
 				s_in.sin_addr = c->ip4.addr_seen;
 		}
 
-		if (!(s = udp_tap_map[V4][src].sock)) {
+		debug("UDP from tap src=%hu dst=%hu, s=%d",
+		      src, dst, udp_tap_map[V4][src].sock);
+		if ((s = udp_tap_map[V4][src].sock) < 0) {
 			union udp_epoll_ref uref = { .port = src };
 			in_addr_t bind_addr = { 0 };
 			const char *bind_if = NULL;
@@ -899,7 +915,7 @@ int udp_tap_handler(struct ctx *c, uint8_t pif,
 			bind_addr = &c->ip6.addr_ll;
 		}
 
-		if (!(s = udp_tap_map[V6][src].sock)) {
+		if ((s = udp_tap_map[V6][src].sock) < 0) {
 			union udp_epoll_ref uref = { .v6 = 1, .port = src };
 			const char *bind_if = NULL;
 
@@ -1161,7 +1177,7 @@ static void udp_timer_one(struct ctx *c, int v6, enum udp_act_type type,
 		return;
 	}
 
-	if (s > 0) {
+	if (s >= 0) {
 		epoll_ctl(c->epollfd, EPOLL_CTL_DEL, s, NULL);
 		close(s);
 		bitmap_clear(udp_act[v6 ? V6 : V4][type], port);
diff --git a/udp.h b/udp.h
index 4e45919..85ebaaa 100644
--- a/udp.h
+++ b/udp.h
@@ -8,6 +8,7 @@
 
 #define UDP_TIMER_INTERVAL		1000 /* ms */
 
+void udp_portmap_clear(void);
 void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events,
 		      const struct timespec *now);
 int udp_tap_handler(struct ctx *c, uint8_t pif, int af,