diff --git a/handshake_messages.go b/handshake_messages.go
index 52fcf02..3653035 100644
--- a/handshake_messages.go
+++ b/handshake_messages.go
@@ -1005,6 +1005,7 @@ type encryptedExtensionsMsg struct {
 	quicTransportParameters []byte
 	earlyData               bool
 	echRetryConfigs         []byte
+	serverNameAck           bool
 }
 
 func (m *encryptedExtensionsMsg) marshal() ([]byte, error) {
@@ -1040,6 +1041,10 @@ func (m *encryptedExtensionsMsg) marshal() ([]byte, error) {
 					b.AddBytes(m.echRetryConfigs)
 				})
 			}
+			if m.serverNameAck {
+				b.AddUint16(extensionServerName)
+				b.AddUint16(0) // empty extension_data
+			}
 		})
 	})
 
@@ -1095,6 +1100,11 @@ func (m *encryptedExtensionsMsg) unmarshal(data []byte) bool {
 			if !extData.CopyBytes(m.echRetryConfigs) {
 				return false
 			}
+		case extensionServerName:
+			if len(extData) != 0 {
+				return false
+			}
+			m.serverNameAck = true
 		default:
 			// Ignore unknown extensions.
 			continue
diff --git a/handshake_server.go b/handshake_server.go
index cb895da..3a2ca85 100644
--- a/handshake_server.go
+++ b/handshake_server.go
@@ -581,6 +581,10 @@ func (hs *serverHandshakeState) doFullHandshake() error {
 		hs.hello.ocspStapling = true
 	}
 
+	if hs.clientHello.serverName != "" {
+		hs.hello.serverNameAck = true
+	}
+
 	hs.hello.ticketSupported = hs.clientHello.ticketSupported && !c.config.SessionTicketsDisabled
 	hs.hello.cipherSuite = hs.suite.id
 
diff --git a/handshake_server_tls13.go b/handshake_server_tls13.go
index ecbfd74..41e303e 100644
--- a/handshake_server_tls13.go
+++ b/handshake_server_tls13.go
@@ -900,6 +900,10 @@ func (hs *serverHandshakeStateTLS13) sendServerParameters() error {
 		encryptedExtensions.earlyData = hs.earlyData
 	}
 
+	if !hs.c.didResume && hs.clientHello.serverName != "" {
+		encryptedExtensions.serverNameAck = true
+	}
+
 	// If client sent ECH extension, but we didn't accept it,
 	// send retry configs, if available.
 	echKeys := hs.c.config.EncryptedClientHelloKeys