diff --git a/conn.go b/conn.go
index 89f0811..f13038d 100644
--- a/conn.go
+++ b/conn.go
@@ -3,6 +3,7 @@ package soju
 import (
 	"fmt"
 	"net"
+	"sync"
 	"time"
 
 	"gopkg.in/irc.v3"
@@ -20,12 +21,14 @@ func setKeepAlive(c net.Conn) error {
 }
 
 type conn struct {
-	net      net.Conn
-	irc      *irc.Conn
-	srv      *Server
-	logger   Logger
+	net    net.Conn
+	irc    *irc.Conn
+	srv    *Server
+	logger Logger
+
+	lock     sync.Mutex
 	outgoing chan<- *irc.Message
-	closed   chan struct{}
+	closed   bool
 }
 
 func newConn(srv *Server, netConn net.Conn, logger Logger) *conn {
@@ -38,7 +41,6 @@ func newConn(srv *Server, netConn net.Conn, logger Logger) *conn {
 		srv:      srv,
 		outgoing: outgoing,
 		logger:   logger,
-		closed:   make(chan struct{}),
 	}
 
 	go func() {
@@ -68,20 +70,21 @@ func newConn(srv *Server, netConn net.Conn, logger Logger) *conn {
 }
 
 func (c *conn) isClosed() bool {
-	select {
-	case <-c.closed:
-		return true
-	default:
-		return false
-	}
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	return c.closed
 }
 
 // Close closes the connection. It is safe to call from any goroutine.
 func (c *conn) Close() error {
-	if c.isClosed() {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	if c.closed {
 		return fmt.Errorf("connection already closed")
 	}
-	close(c.closed)
+
+	c.closed = true
 	close(c.outgoing)
 	return nil
 }
@@ -101,8 +104,14 @@ func (c *conn) ReadMessage() (*irc.Message, error) {
 
 // SendMessage queues a new outgoing message. It is safe to call from any
 // goroutine.
+//
+// If the connection is closed before the message is sent, SendMessage silently
+// drops the message.
 func (c *conn) SendMessage(msg *irc.Message) {
-	if c.isClosed() {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	if c.closed {
 		return
 	}
 	c.outgoing <- msg