diff --git a/port_fwd.c b/port_fwd.c
index eac8d2f..7943a30 100644
--- a/port_fwd.c
+++ b/port_fwd.c
@@ -86,22 +86,33 @@ void port_fwd_scan_tcp(struct port_fwd *fwd, const struct port_fwd *rev)
  * port_fwd_scan_tcp() - Scan /proc to update TCP forwarding map
  * @fwd:	Forwarding information to update
  * @rev:	Forwarding information for the reverse direction
- * @tcp:	Corresponding TCP forwarding information
+ * @tcp_fwd:	Corresponding TCP forwarding information
+ * @tcp_rev:	TCP forwarding information for the reverse direction
  */
 void port_fwd_scan_udp(struct port_fwd *fwd, const struct port_fwd *rev,
-		       const struct port_fwd *tcp)
+		       const struct port_fwd *tcp_fwd,
+		       const struct port_fwd *tcp_rev)
 {
+	uint8_t exclude[PORT_BITMAP_SIZE];
+
+	bitmap_or(exclude, PORT_BITMAP_SIZE, rev->map, tcp_rev->map);
+
 	memset(fwd->map, 0, PORT_BITMAP_SIZE);
-	procfs_scan_listen(fwd->scan4, UDP_LISTEN, fwd->map, rev->map);
-	procfs_scan_listen(fwd->scan6, UDP_LISTEN, fwd->map, rev->map);
+	procfs_scan_listen(fwd->scan4, UDP_LISTEN, fwd->map, exclude);
+	procfs_scan_listen(fwd->scan6, UDP_LISTEN, fwd->map, exclude);
 
 	/* Also forward UDP ports with the same numbers as bound TCP ports.
 	 * This is useful for a handful of protocols (e.g. iperf3) where a TCP
 	 * control port is used to set up transfers on a corresponding UDP
 	 * port.
+	 *
+	 * This means we need to skip numbers of TCP ports bound on the other
+	 * side, too. Otherwise, we would detect corresponding UDP ports as
+	 * bound and try to forward them from the opposite side, but it's
+	 * already us handling them.
 	 */
-	procfs_scan_listen(tcp->scan4, TCP_LISTEN, fwd->map, rev->map);
-	procfs_scan_listen(tcp->scan6, TCP_LISTEN, fwd->map, rev->map);
+	procfs_scan_listen(tcp_fwd->scan4, TCP_LISTEN, fwd->map, exclude);
+	procfs_scan_listen(tcp_fwd->scan6, TCP_LISTEN, fwd->map, exclude);
 }
 
 /**
@@ -126,7 +137,7 @@ void port_fwd_init(struct ctx *c)
 		c->udp.fwd_in.f.scan4 = open_in_ns(c, "/proc/net/udp", flags);
 		c->udp.fwd_in.f.scan6 = open_in_ns(c, "/proc/net/udp6", flags);
 		port_fwd_scan_udp(&c->udp.fwd_in.f, &c->udp.fwd_out.f,
-				  &c->tcp.fwd_in);
+				  &c->tcp.fwd_in, &c->tcp.fwd_out);
 	}
 	if (c->tcp.fwd_out.mode == FWD_AUTO) {
 		c->tcp.fwd_out.scan4 = open("/proc/net/tcp", flags);
@@ -137,6 +148,6 @@ void port_fwd_init(struct ctx *c)
 		c->udp.fwd_out.f.scan4 = open("/proc/net/udp", flags);
 		c->udp.fwd_out.f.scan6 = open("/proc/net/udp6", flags);
 		port_fwd_scan_udp(&c->udp.fwd_out.f, &c->udp.fwd_in.f,
-				  &c->tcp.fwd_out);
+				  &c->tcp.fwd_out, &c->tcp.fwd_in);
 	}
 }
diff --git a/port_fwd.h b/port_fwd.h
index 8a823d8..f6bf1b5 100644
--- a/port_fwd.h
+++ b/port_fwd.h
@@ -37,7 +37,8 @@ struct port_fwd {
 
 void port_fwd_scan_tcp(struct port_fwd *fwd, const struct port_fwd *rev);
 void port_fwd_scan_udp(struct port_fwd *fwd, const struct port_fwd *rev,
-		       const struct port_fwd *tcp);
+		       const struct port_fwd *tcp_fwd,
+		       const struct port_fwd *tcp_rev);
 void port_fwd_init(struct ctx *c);
 
 #endif /* PORT_FWD_H */
diff --git a/udp.c b/udp.c
index cc1ea9c..1f8c306 100644
--- a/udp.c
+++ b/udp.c
@@ -1260,13 +1260,13 @@ void udp_timer(struct ctx *c, const struct timespec *ts)
 	if (c->mode == MODE_PASTA) {
 		if (c->udp.fwd_out.f.mode == FWD_AUTO) {
 			port_fwd_scan_udp(&c->udp.fwd_out.f, &c->udp.fwd_in.f,
-					  &c->tcp.fwd_out);
+					  &c->tcp.fwd_out, &c->tcp.fwd_in);
 			NS_CALL(udp_port_rebind_outbound, c);
 		}
 
 		if (c->udp.fwd_in.f.mode == FWD_AUTO) {
 			port_fwd_scan_udp(&c->udp.fwd_in.f, &c->udp.fwd_out.f,
-					  &c->tcp.fwd_in);
+					  &c->tcp.fwd_in, &c->tcp.fwd_out);
 			udp_port_rebind(c, false);
 		}
 	}
diff --git a/util.c b/util.c
index c38ab7e..d465e48 100644
--- a/util.c
+++ b/util.c
@@ -325,6 +325,27 @@ int bitmap_isset(const uint8_t *map, int bit)
 	return !!(*word & BITMAP_BIT(bit));
 }
 
+/**
+ * bitmap_or() - Logical disjunction (OR) of two bitmaps
+ * @dst:	Pointer to result bitmap
+ * @size:	Size of bitmaps, in bytes
+ * @a:		First operand
+ * @b:		Second operand
+ */
+void bitmap_or(uint8_t *dst, size_t size, const uint8_t *a, const uint8_t *b)
+{
+	unsigned long *dw = (unsigned long *)dst;
+	unsigned long *aw = (unsigned long *)a;
+	unsigned long *bw = (unsigned long *)b;
+	size_t i;
+
+	for (i = 0; i < size / sizeof(long); i++, dw++, aw++, bw++)
+		*dw = *aw | *bw;
+
+	for (i = size / sizeof(long) * sizeof(long); i < size; i++)
+		dst[i] = a[i] | b[i];
+}
+
 /*
  * ns_enter() - Enter configured user (unless already joined) and network ns
  * @c:		Execution context
diff --git a/util.h b/util.h
index 78a8fb2..1f02588 100644
--- a/util.h
+++ b/util.h
@@ -216,6 +216,7 @@ int timespec_diff_ms(const struct timespec *a, const struct timespec *b);
 void bitmap_set(uint8_t *map, int bit);
 void bitmap_clear(uint8_t *map, int bit);
 int bitmap_isset(const uint8_t *map, int bit);
+void bitmap_or(uint8_t *dst, size_t size, const uint8_t *a, const uint8_t *b);
 char *line_read(char *buf, size_t len, int fd);
 void ns_enter(const struct ctx *c);
 bool ns_is_init(void);