diff --git a/src/pkg/http/client.go b/src/pkg/http/client.go
index 82fff780016..c24eea58191 100644
--- a/src/pkg/http/client.go
+++ b/src/pkg/http/client.go
@@ -117,7 +117,7 @@ func send(req *Request, t Transport) (resp *Response, err os.Error) {
 	// Headers, leaving it uninitialized.  We guarantee to the
 	// Transport that this has been initialized, though.
 	if req.Header == nil {
-		req.Header = Header(make(map[string][]string))
+		req.Header = make(Header)
 	}
 
 	info := req.URL.RawUserinfo
diff --git a/src/pkg/http/readrequest_test.go b/src/pkg/http/readrequest_test.go
index 6ee07bc9148..19e2ff77476 100644
--- a/src/pkg/http/readrequest_test.go
+++ b/src/pkg/http/readrequest_test.go
@@ -93,7 +93,7 @@ var reqTests = []reqTest{
 			Proto:         "HTTP/1.1",
 			ProtoMajor:    1,
 			ProtoMinor:    1,
-			Header:        map[string][]string{},
+			Header:        Header{},
 			Close:         false,
 			ContentLength: -1,
 			Host:          "test",
diff --git a/src/pkg/http/request.go b/src/pkg/http/request.go
index 2f6e33ae9b0..d8456bab321 100644
--- a/src/pkg/http/request.go
+++ b/src/pkg/http/request.go
@@ -247,7 +247,7 @@ func (req *Request) write(w io.Writer, usingProxy bool) os.Error {
 	// from Request, and introduce Request methods along the lines of
 	// Response.{GetHeader,AddHeader} and string constants for "Host",
 	// "User-Agent" and "Referer".
-	err = writeSortedKeyValue(w, req.Header, reqExcludeHeader)
+	err = writeSortedHeader(w, req.Header, reqExcludeHeader)
 	if err != nil {
 		return err
 	}
diff --git a/src/pkg/http/requestwrite_test.go b/src/pkg/http/requestwrite_test.go
index a0cc4606663..03a766efd8c 100644
--- a/src/pkg/http/requestwrite_test.go
+++ b/src/pkg/http/requestwrite_test.go
@@ -84,7 +84,7 @@ var reqWriteTests = []reqWriteTest{
 			},
 			ProtoMajor:       1,
 			ProtoMinor:       1,
-			Header:           map[string][]string{},
+			Header:           Header{},
 			TransferEncoding: []string{"chunked"},
 		},
 
@@ -112,7 +112,7 @@ var reqWriteTests = []reqWriteTest{
 			},
 			ProtoMajor:       1,
 			ProtoMinor:       1,
-			Header:           map[string][]string{},
+			Header:           Header{},
 			Close:            true,
 			TransferEncoding: []string{"chunked"},
 		},
diff --git a/src/pkg/http/response.go b/src/pkg/http/response.go
index 4fd00ad61ea..3d77c555510 100644
--- a/src/pkg/http/response.go
+++ b/src/pkg/http/response.go
@@ -67,10 +67,9 @@ type Response struct {
 	// ReadResponse nor Response.Write ever closes a connection.
 	Close bool
 
-	// Trailer maps trailer keys to values.  Like for Header, if the
-	// response has multiple trailer lines with the same key, they will be
-	// concatenated, delimited by commas.
-	Trailer map[string][]string
+	// Trailer maps trailer keys to values, in the same
+	// format as the header.
+	Trailer Header
 }
 
 // ReadResponse reads and returns an HTTP response from r.  The RequestMethod
@@ -193,7 +192,7 @@ func (resp *Response) Write(w io.Writer) os.Error {
 	}
 
 	// Rest of header
-	err = writeSortedKeyValue(w, resp.Header, respExcludeHeader)
+	err = writeSortedHeader(w, resp.Header, respExcludeHeader)
 	if err != nil {
 		return err
 	}
@@ -215,16 +214,16 @@ func (resp *Response) Write(w io.Writer) os.Error {
 	return nil
 }
 
-func writeSortedKeyValue(w io.Writer, kvm map[string][]string, exclude map[string]bool) os.Error {
-	keys := make([]string, 0, len(kvm))
-	for k := range kvm {
+func writeSortedHeader(w io.Writer, h Header, exclude map[string]bool) os.Error {
+	keys := make([]string, 0, len(h))
+	for k := range h {
 		if !exclude[k] {
 			keys = append(keys, k)
 		}
 	}
 	sort.SortStrings(keys)
 	for _, k := range keys {
-		for _, v := range kvm[k] {
+		for _, v := range h[k] {
 			if _, err := fmt.Fprintf(w, "%s: %s\r\n", k, v); err != nil {
 				return err
 			}
diff --git a/src/pkg/http/responsewrite_test.go b/src/pkg/http/responsewrite_test.go
index aabb833f9c8..228ed5f7d1e 100644
--- a/src/pkg/http/responsewrite_test.go
+++ b/src/pkg/http/responsewrite_test.go
@@ -22,7 +22,7 @@ var respWriteTests = []respWriteTest{
 			ProtoMajor:    1,
 			ProtoMinor:    0,
 			RequestMethod: "GET",
-			Header:        map[string][]string{},
+			Header:        Header{},
 			Body:          nopCloser{bytes.NewBufferString("abcdef")},
 			ContentLength: 6,
 		},
@@ -38,7 +38,7 @@ var respWriteTests = []respWriteTest{
 			ProtoMajor:    1,
 			ProtoMinor:    0,
 			RequestMethod: "GET",
-			Header:        map[string][]string{},
+			Header:        Header{},
 			Body:          nopCloser{bytes.NewBufferString("abcdef")},
 			ContentLength: -1,
 		},
@@ -53,7 +53,7 @@ var respWriteTests = []respWriteTest{
 			ProtoMajor:       1,
 			ProtoMinor:       1,
 			RequestMethod:    "GET",
-			Header:           map[string][]string{},
+			Header:           Header{},
 			Body:             nopCloser{bytes.NewBufferString("abcdef")},
 			ContentLength:    6,
 			TransferEncoding: []string{"chunked"},