diff --git a/core/dns.go b/core/dns.go
index 5107bbc80..1cd9ba147 100644
--- a/core/dns.go
+++ b/core/dns.go
@@ -127,6 +127,7 @@ func NewDNSResolverImpl(dialTimeout time.Duration, servers []string) *DNSResolve
 
 	// Set timeout for underlying net.Conn
 	dnsClient.DialTimeout = dialTimeout
+	dnsClient.Net = "tcp"
 
 	return &DNSResolverImpl{
 		DNSClient:                dnsClient,
diff --git a/core/dns_test.go b/core/dns_test.go
index 559fe506a..33272b2f5 100644
--- a/core/dns_test.go
+++ b/core/dns_test.go
@@ -21,7 +21,6 @@ import (
 const dnsLoopbackAddr = "127.0.0.1:4053"
 
 func mockDNSQuery(w dns.ResponseWriter, r *dns.Msg) {
-	defer w.Close()
 	m := new(dns.Msg)
 	m.SetReply(r)
 	m.Compress = false
@@ -114,7 +113,7 @@ func mockDNSQuery(w dns.ResponseWriter, r *dns.Msg) {
 
 func serveLoopResolver(stopChan chan bool) chan bool {
 	dns.HandleFunc(".", mockDNSQuery)
-	server := &dns.Server{Addr: dnsLoopbackAddr, Net: "udp", ReadTimeout: time.Millisecond, WriteTimeout: time.Millisecond}
+	server := &dns.Server{Addr: dnsLoopbackAddr, Net: "tcp", ReadTimeout: time.Millisecond, WriteTimeout: time.Millisecond}
 	waitChan := make(chan bool, 1)
 	go func() {
 		waitChan <- true
diff --git a/test/dns-test-srv/main.go b/test/dns-test-srv/main.go
index d3931e8e9..7621119d5 100644
--- a/test/dns-test-srv/main.go
+++ b/test/dns-test-srv/main.go
@@ -15,7 +15,6 @@ import (
 )
 
 func dnsHandler(w dns.ResponseWriter, r *dns.Msg) {
-	defer w.Close()
 	m := new(dns.Msg)
 	m.SetReply(r)
 	m.Compress = false
@@ -65,7 +64,7 @@ func serveTestResolver() {
 	dns.HandleFunc(".", dnsHandler)
 	server := &dns.Server{
 		Addr:         "127.0.0.1:8053",
-		Net:          "udp",
+		Net:          "tcp",
 		ReadTimeout:  time.Millisecond,
 		WriteTimeout: time.Millisecond,
 	}