diff --git a/header.go b/header.go
index 19eb914..f86fc60 100644
--- a/header.go
+++ b/header.go
@@ -46,6 +46,9 @@ type ResponseHeader struct {
 	ContentLength   int
 	ConnectionClose bool
 
+	contentType []byte
+	server      []byte
+
 	h     []argsKV
 	bufKV argsKV
 }
@@ -55,6 +58,9 @@ type RequestHeader struct {
 	RequestURI    []byte
 	ContentLength int
 
+	host        []byte
+	contentType []byte
+
 	h     []argsKV
 	bufKV argsKV
 }
@@ -76,6 +82,9 @@ func (h *ResponseHeader) Clear() {
 	h.ContentLength = 0
 	h.ConnectionClose = false
 
+	h.contentType = h.contentType[:0]
+	h.server = h.server[:0]
+
 	h.h = h.h[:0]
 }
 
@@ -84,6 +93,9 @@ func (h *RequestHeader) Clear() {
 	h.RequestURI = h.RequestURI[:0]
 	h.ContentLength = 0
 
+	h.host = h.host[:0]
+	h.contentType = h.contentType[:0]
+
 	h.h = h.h[:0]
 }
 
@@ -94,6 +106,10 @@ func (h *ResponseHeader) Set(key, value string) {
 
 func (h *ResponseHeader) set(key, value []byte) {
 	switch {
+	case bytes.Equal(strContentType, key):
+		h.contentType = append(h.contentType[:0], value...)
+	case bytes.Equal(strServer, key):
+		h.server = append(h.server[:0], value...)
 	case bytes.Equal(strContentLength, key):
 		// skip Conent-Length setting, since it will be set automatically.
 	case bytes.Equal(strConnection, key):
@@ -127,6 +143,10 @@ func (h *RequestHeader) Set(key, value string) {
 
 func (h *RequestHeader) set(key, value []byte) {
 	switch {
+	case bytes.Equal(strHost, key):
+		h.host = append(h.host[:0], value...)
+	case bytes.Equal(strContentType, key):
+		h.contentType = append(h.contentType[:0], value...)
 	case bytes.Equal(strContentLength, key):
 		// Content-Length is managed automatically.
 	case bytes.Equal(strTransferEncoding, key):
@@ -154,17 +174,30 @@ func (h *RequestHeader) Peek(key string) []byte {
 }
 
 func (h *ResponseHeader) peek(key []byte) []byte {
-	if bytes.Equal(strConnection, key) {
+	switch {
+	case bytes.Equal(strContentType, key):
+		return h.contentType
+	case bytes.Equal(strServer, key):
+		return h.server
+	case bytes.Equal(strConnection, key):
 		if h.ConnectionClose {
 			return strClose
 		}
 		return nil
+	default:
+		return peekKV(h.h, key)
 	}
-	return peekKV(h.h, key)
 }
 
 func (h *RequestHeader) peek(key []byte) []byte {
-	return peekKV(h.h, key)
+	switch {
+	case bytes.Equal(strHost, key):
+		return h.host
+	case bytes.Equal(strContentType, key):
+		return h.contentType
+	default:
+		return peekKV(h.h, key)
+	}
 }
 
 func (h *ResponseHeader) Get(key string) string {
@@ -293,14 +326,14 @@ func (h *ResponseHeader) Write(w *bufio.Writer) error {
 	}
 	w.Write(statusLine(statusCode))
 
-	server := h.peek(strServer)
+	server := h.server
 	if len(server) == 0 {
 		server = defaultServerName
 	}
 	writeHeaderLine(w, strServer, server)
 	writeHeaderLine(w, strDate, serverDate.Load().([]byte))
 
-	contentType := h.peek(strContentType)
+	contentType := h.contentType
 	if len(contentType) == 0 {
 		contentType = defaultContentType
 	}
@@ -341,14 +374,14 @@ func (h *RequestHeader) Write(w *bufio.Writer) error {
 	w.Write(strHTTP11)
 	w.Write(strCRLF)
 
-	host := h.peek(strHost)
+	host := h.host
 	if len(host) == 0 {
 		return fmt.Errorf("missing required Host header")
 	}
 	writeHeaderLine(w, strHost, host)
 
 	if h.IsMethodPost() {
-		contentType := h.peek(strContentType)
+		contentType := h.contentType
 		if len(contentType) == 0 {
 			return fmt.Errorf("missing required Content-Type header for POST request")
 		}
@@ -384,20 +417,6 @@ func writeContentLength(w *bufio.Writer, contentLength int) {
 	w.Write(strCRLF)
 }
 
-func mustPeekBuffered(r *bufio.Reader) []byte {
-	buf, err := r.Peek(r.Buffered())
-	if len(buf) == 0 || err != nil {
-		panic(fmt.Sprintf("bufio.Reader.Peek() returned unexpected data (%q, %v)", buf, err))
-	}
-	return buf
-}
-
-func mustDiscard(r *bufio.Reader, n int) {
-	if _, err := r.Discard(n); err != nil {
-		panic(fmt.Sprintf("bufio.Reader.Discard(%d) failed: %s", n, err))
-	}
-}
-
 func (h *ResponseHeader) parse(buf []byte) (b []byte, err error) {
 	b, err = h.parseFirstLine(buf)
 	if err != nil {
@@ -477,6 +496,10 @@ func (h *ResponseHeader) parseHeaders(buf []byte) ([]byte, error) {
 	var err error
 	for p.next() {
 		switch {
+		case bytes.Equal(p.key, strContentType):
+			h.contentType = append(h.contentType[:0], p.value...)
+		case bytes.Equal(p.key, strServer):
+			h.server = append(h.server[:0], p.value...)
 		case bytes.Equal(p.key, strContentLength):
 			if h.ContentLength != -1 {
 				h.ContentLength, err = parseContentLength(p.value)
@@ -503,7 +526,7 @@ func (h *ResponseHeader) parseHeaders(buf []byte) ([]byte, error) {
 		return nil, p.err
 	}
 
-	if len(h.peek(strContentType)) == 0 {
+	if len(h.contentType) == 0 {
 		return nil, fmt.Errorf("missing required Content-Type header in %q", buf)
 	}
 	if h.ContentLength == -2 {
@@ -520,6 +543,10 @@ func (h *RequestHeader) parseHeaders(buf []byte) ([]byte, error) {
 	var err error
 	for p.next() {
 		switch {
+		case bytes.Equal(p.key, strHost):
+			h.host = append(h.host[:0], p.value...)
+		case bytes.Equal(p.key, strContentType):
+			h.contentType = append(h.contentType[:0], p.value...)
 		case bytes.Equal(p.key, strContentLength):
 			if h.ContentLength != -1 {
 				h.ContentLength, err = parseContentLength(p.value)
@@ -542,11 +569,11 @@ func (h *RequestHeader) parseHeaders(buf []byte) ([]byte, error) {
 		return nil, p.err
 	}
 
-	if len(h.peek(strHost)) == 0 {
+	if len(h.host) == 0 {
 		return nil, fmt.Errorf("missing required Host header in %q", buf)
 	}
 	if h.IsMethodPost() {
-		if len(h.peek(strContentType)) == 0 {
+		if len(h.contentType) == 0 {
 			return nil, fmt.Errorf("missing Content-Type for POST header in %q", buf)
 		}
 		if h.ContentLength == -2 {
@@ -671,3 +698,17 @@ func isNeedMoreError(err error) bool {
 	_, ok := err.(*errNeedMore)
 	return ok
 }
+
+func mustPeekBuffered(r *bufio.Reader) []byte {
+	buf, err := r.Peek(r.Buffered())
+	if len(buf) == 0 || err != nil {
+		panic(fmt.Sprintf("bufio.Reader.Peek() returned unexpected data (%q, %v)", buf, err))
+	}
+	return buf
+}
+
+func mustDiscard(r *bufio.Reader, n int) {
+	if _, err := r.Discard(n); err != nil {
+		panic(fmt.Sprintf("bufio.Reader.Discard(%d) failed: %s", n, err))
+	}
+}