diff --git a/adapters/outbound/util.go b/adapters/outbound/util.go
index 79229916..8d617968 100644
--- a/adapters/outbound/util.go
+++ b/adapters/outbound/util.go
@@ -115,8 +115,9 @@ func dialTimeout(network, address string, timeout time.Duration) (net.Conn, erro
 	type dialResult struct {
 		net.Conn
 		error
-		ipv6 bool
-		done bool
+		resolved bool
+		ipv6     bool
+		done     bool
 	}
 	results := make(chan dialResult)
 	var primary, fallback dialResult
@@ -142,6 +143,7 @@ func dialTimeout(network, address string, timeout time.Duration) (net.Conn, erro
 		if result.error != nil {
 			return
 		}
+		result.resolved = true
 
 		if ipv6 {
 			result.Conn, result.error = dialer.DialContext(ctx, "tcp6", net.JoinHostPort(ip.String(), port))
@@ -160,14 +162,20 @@ func dialTimeout(network, address string, timeout time.Duration) (net.Conn, erro
 				return res.Conn, nil
 			}
 
-			if res.ipv6 {
+			if !res.ipv6 {
 				primary = res
 			} else {
 				fallback = res
 			}
 
 			if primary.done && fallback.done {
-				return nil, primary.error
+				if primary.resolved {
+					return nil, primary.error
+				} else if fallback.resolved {
+					return nil, fallback.error
+				} else {
+					return nil, primary.error
+				}
 			}
 		}
 	}
diff --git a/dns/iputil.go b/dns/iputil.go
index 66dd0c0e..7967b44a 100644
--- a/dns/iputil.go
+++ b/dns/iputil.go
@@ -3,10 +3,12 @@ package dns
 import (
 	"errors"
 	"net"
+	"strings"
 )
 
 var (
 	errIPNotFound = errors.New("cannot found ip")
+	errIPVersion  = errors.New("ip version error")
 )
 
 // ResolveIPv4 with a host, return ipv4
@@ -18,8 +20,11 @@ func ResolveIPv4(host string) (net.IP, error) {
 	}
 
 	ip := net.ParseIP(host)
-	if ip4 := ip.To4(); ip4 != nil {
-		return ip4, nil
+	if ip != nil {
+		if !strings.Contains(host, ":") {
+			return ip, nil
+		}
+		return nil, errIPVersion
 	}
 
 	if DefaultResolver != nil {
@@ -32,8 +37,8 @@ func ResolveIPv4(host string) (net.IP, error) {
 	}
 
 	for _, ip := range ipAddrs {
-		if ip4 := ip.To4(); ip4 != nil {
-			return ip4, nil
+		if len(ip) == net.IPv4len {
+			return ip, nil
 		}
 	}
 
@@ -49,8 +54,11 @@ func ResolveIPv6(host string) (net.IP, error) {
 	}
 
 	ip := net.ParseIP(host)
-	if ip6 := ip.To16(); ip6 != nil {
-		return ip6, nil
+	if ip != nil {
+		if strings.Contains(host, ":") {
+			return ip, nil
+		}
+		return nil, errIPVersion
 	}
 
 	if DefaultResolver != nil {
@@ -63,8 +71,8 @@ func ResolveIPv6(host string) (net.IP, error) {
 	}
 
 	for _, ip := range ipAddrs {
-		if ip6 := ip.To16(); ip6 != nil {
-			return ip6, nil
+		if len(ip) == net.IPv6len {
+			return ip, nil
 		}
 	}
 
diff --git a/dns/resolver.go b/dns/resolver.go
index a9cd283e..0ba23420 100644
--- a/dns/resolver.go
+++ b/dns/resolver.go
@@ -221,13 +221,11 @@ func (r *Resolver) fallbackExchange(m *D.Msg) (msg *D.Msg, err error) {
 
 func (r *Resolver) resolveIP(host string, dnsType uint16) (ip net.IP, err error) {
 	ip = net.ParseIP(host)
-	if dnsType == D.TypeAAAA {
-		if ip6 := ip.To16(); ip6 != nil {
-			return ip6, nil
-		}
-	} else {
-		if ip4 := ip.To4(); ip4 != nil {
-			return ip4, nil
+	if ip != nil {
+		if dnsType == D.TypeAAAA && len(ip) == net.IPv6len {
+			return ip, nil
+		} else if dnsType == D.TypeA && len(ip) == net.IPv4len {
+			return ip, nil
 		}
 	}