diff --git a/codec/codec.go b/codec/codec.go
index dad14d4a..1052d8e2 100644
--- a/codec/codec.go
+++ b/codec/codec.go
@@ -38,9 +38,9 @@ type MessageType int
 // connection. ReadBody may be called with a nil argument to force the
 // body to be read and discarded.
 type Codec interface {
-	ReadHeader(io.ReadWriter, *Message, MessageType) error
-	ReadBody(io.ReadWriter, interface{}) error
-	Write(io.ReadWriter, *Message, interface{}) error
+	ReadHeader(io.Reader, *Message, MessageType) error
+	ReadBody(io.Reader, interface{}) error
+	Write(io.Writer, *Message, interface{}) error
 	Marshal(interface{}) ([]byte, error)
 	Unmarshal([]byte, interface{}) error
 	String() string
diff --git a/codec/noop.go b/codec/noop.go
index 02a0e12f..129c89bd 100644
--- a/codec/noop.go
+++ b/codec/noop.go
@@ -13,11 +13,11 @@ type Frame struct {
 	Data []byte
 }
 
-func (c *noopCodec) ReadHeader(conn io.ReadWriter, m *Message, t MessageType) error {
+func (c *noopCodec) ReadHeader(conn io.Reader, m *Message, t MessageType) error {
 	return nil
 }
 
-func (c *noopCodec) ReadBody(conn io.ReadWriter, b interface{}) error {
+func (c *noopCodec) ReadBody(conn io.Reader, b interface{}) error {
 	// read bytes
 	buf, err := ioutil.ReadAll(conn)
 	if err != nil {
@@ -46,7 +46,7 @@ func (c *noopCodec) ReadBody(conn io.ReadWriter, b interface{}) error {
 	return nil
 }
 
-func (c *noopCodec) Write(conn io.ReadWriter, m *Message, b interface{}) error {
+func (c *noopCodec) Write(conn io.Writer, m *Message, b interface{}) error {
 	if b == nil {
 		return nil
 	}