diff --git a/app/cmd/client.go b/app/cmd/client.go
index 1240980..7277e12 100644
--- a/app/cmd/client.go
+++ b/app/cmd/client.go
@@ -12,8 +12,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/apernet/hysteria/extras/transport/udphop"
-
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 	"go.uber.org/zap"
@@ -26,6 +24,7 @@ import (
 	"github.com/apernet/hysteria/app/internal/utils"
 	"github.com/apernet/hysteria/core/client"
 	"github.com/apernet/hysteria/extras/obfs"
+	"github.com/apernet/hysteria/extras/transport/udphop"
 )
 
 // Client flags
diff --git a/extras/transport/udphop/addr.go b/extras/transport/udphop/addr.go
index ccbe3cb..3c70472 100644
--- a/extras/transport/udphop/addr.go
+++ b/extras/transport/udphop/addr.go
@@ -1,13 +1,19 @@
 package udphop
 
 import (
-	"errors"
+	"fmt"
 	"net"
 	"strconv"
 	"strings"
 )
 
-var ErrInvalidPort = errors.New("invalid port")
+type InvalidPortError struct {
+	PortStr string
+}
+
+func (e InvalidPortError) Error() string {
+	return fmt.Sprintf("%s is not a valid port number or range", e.PortStr)
+}
 
 // UDPHopAddr contains an IP address and a list of ports.
 type UDPHopAddr struct {
@@ -57,15 +63,15 @@ func ResolveUDPHopAddr(addr string) (*UDPHopAddr, error) {
 			// Port range
 			portRange := strings.Split(portStr, "-")
 			if len(portRange) != 2 {
-				return nil, ErrInvalidPort
+				return nil, InvalidPortError{portStr}
 			}
 			start, err := strconv.ParseUint(portRange[0], 10, 16)
 			if err != nil {
-				return nil, ErrInvalidPort
+				return nil, InvalidPortError{portStr}
 			}
 			end, err := strconv.ParseUint(portRange[1], 10, 16)
 			if err != nil {
-				return nil, ErrInvalidPort
+				return nil, InvalidPortError{portStr}
 			}
 			if start > end {
 				start, end = end, start
@@ -77,7 +83,7 @@ func ResolveUDPHopAddr(addr string) (*UDPHopAddr, error) {
 			// Single port
 			port, err := strconv.ParseUint(portStr, 10, 16)
 			if err != nil {
-				return nil, ErrInvalidPort
+				return nil, InvalidPortError{portStr}
 			}
 			result.Ports = append(result.Ports, uint16(port))
 		}