diff --git a/http.go b/http.go
index 0531a80..bd716a0 100644
--- a/http.go
+++ b/http.go
@@ -41,7 +41,7 @@ type httpClient struct {
 	funcStream client.FuncStream
 	httpcli    *http.Client
 	opts       client.Options
-	sync.RWMutex
+	mu         sync.RWMutex
 }
 
 func newRequest(ctx context.Context, log logger.Logger, addr string, req client.Request, ct string, cf codec.Codec, msg interface{}, opts client.CallOptions) (*http.Request, error) {
@@ -294,18 +294,18 @@ func (c *httpClient) stream(ctx context.Context, addr string, req client.Request
 }
 
 func (c *httpClient) newCodec(ct string) (codec.Codec, error) {
-	c.RLock()
+	c.mu.RLock()
 
 	if idx := strings.IndexRune(ct, ';'); idx >= 0 {
 		ct = ct[:idx]
 	}
 
 	if cf, ok := c.opts.Codecs[ct]; ok {
-		c.RUnlock()
+		c.mu.RUnlock()
 		return cf, nil
 	}
 
-	c.RUnlock()
+	c.mu.RUnlock()
 	return nil, codec.ErrUnknownContentType
 }
 
diff --git a/stream.go b/stream.go
index 9f30103..d5b765c 100644
--- a/stream.go
+++ b/stream.go
@@ -28,7 +28,7 @@ type httpStream struct {
 	address string
 	ct      string
 	opts    client.CallOptions
-	sync.RWMutex
+	mu      sync.RWMutex
 }
 
 var errShutdown = fmt.Errorf("connection is shut down")
@@ -59,8 +59,8 @@ func (h *httpStream) SendMsg(msg interface{}) error {
 }
 
 func (h *httpStream) Send(msg interface{}) error {
-	h.Lock()
-	defer h.Unlock()
+	h.mu.Lock()
+	defer h.mu.Unlock()
 
 	if h.isClosed() {
 		h.err = errShutdown
@@ -80,8 +80,8 @@ func (h *httpStream) RecvMsg(msg interface{}) error {
 }
 
 func (h *httpStream) Recv(msg interface{}) error {
-	h.Lock()
-	defer h.Unlock()
+	h.mu.Lock()
+	defer h.mu.Unlock()
 
 	if h.isClosed() {
 		h.err = errShutdown
@@ -98,8 +98,8 @@ func (h *httpStream) Recv(msg interface{}) error {
 }
 
 func (h *httpStream) Error() error {
-	h.RLock()
-	defer h.RUnlock()
+	h.mu.RLock()
+	defer h.mu.RUnlock()
 	return h.err
 }