diff --git a/src/array.h b/src/array.h
index 359fbbcd..dcb98533 100644
--- a/src/array.h
+++ b/src/array.h
@@ -37,7 +37,6 @@ typedef struct {
 } data_string;
 
 data_string *data_string_init(void);
-data_string *data_response_init(void);
 
 typedef struct {
 	DATA_UNSET;
diff --git a/src/data_string.c b/src/data_string.c
index f9e50d39..e60232fa 100644
--- a/src/data_string.c
+++ b/src/data_string.c
@@ -49,25 +49,6 @@ static int data_string_insert_dup(data_unset *dst, data_unset *src) {
 	return 0;
 }
 
-static int data_response_insert_dup(data_unset *dst, data_unset *src) {
-	data_string *ds_dst = (data_string *)dst;
-	data_string *ds_src = (data_string *)src;
-
-	if (!buffer_is_empty(ds_dst->value)) {
-		buffer_append_string_len(ds_dst->value, CONST_STR_LEN("\r\n"));
-		buffer_append_string_buffer(ds_dst->value, ds_dst->key);
-		buffer_append_string_len(ds_dst->value, CONST_STR_LEN(": "));
-		buffer_append_string_buffer(ds_dst->value, ds_src->value);
-	} else {
-		buffer_copy_buffer(ds_dst->value, ds_src->value);
-	}
-
-	src->free(src);
-
-	return 0;
-}
-
-
 static void data_string_print(const data_unset *d, int depth) {
 	data_string *ds = (data_string *)d;
 	size_t i, len;
@@ -112,12 +93,3 @@ data_string *data_string_init(void) {
 
 	return ds;
 }
-
-data_string *data_response_init(void) {
-	data_string *ds;
-
-	ds = data_string_init();
-	ds->insert_dup = data_response_insert_dup;
-
-	return ds;
-}
diff --git a/src/http-header-glue.c b/src/http-header-glue.c
index 5d4f1f5f..d590ff24 100644
--- a/src/http-header-glue.c
+++ b/src/http-header-glue.c
@@ -27,14 +27,18 @@ int response_header_insert(server *srv, connection *con, const char *key, size_t
 
 	UNUSED(srv);
 
-	if (NULL == (ds = (data_string *)array_get_unused_element(con->response.headers, TYPE_STRING))) {
-		ds = data_response_init();
-	}
-	buffer_copy_string_len(ds->key, key, keylen);
-	buffer_copy_string_len(ds->value, value, vallen);
+	if (0 == vallen) return 0;
 
-	array_insert_unique(con->response.headers, (data_unset *)ds);
+	/* if there already is a key by this name append the value */
+	if (NULL != (ds = (data_string *)array_get_element_klen(con->response.headers, key, keylen))) {
+		buffer_append_string_len(ds->value, CONST_STR_LEN("\r\n"));
+		buffer_append_string_len(ds->value, key, keylen);
+		buffer_append_string_len(ds->value, CONST_STR_LEN(": "));
+		buffer_append_string_len(ds->value, value, vallen);
+		return 0;
+	}
 
+	array_set_key_value(con->response.headers, key, keylen, value, vallen);
 	return 0;
 }
 
@@ -1031,13 +1035,7 @@ static int http_response_process_headers(server *srv, connection *con, http_resp
             break;
         }
 
-        ds = (data_string *)
-          array_get_unused_element(con->response.headers, TYPE_STRING);
-        if (NULL == ds) ds = data_response_init();
-        buffer_copy_string_len(ds->key, key, key_len);
-        buffer_copy_string(ds->value, value);
-
-        array_insert_unique(con->response.headers, (data_unset *)ds);
+        response_header_insert(srv, con, key, key_len, value, strlen(value));
     }
 
     /* CGI/1.1 rev 03 - 7.2.1.2 */
diff --git a/src/mod_usertrack.c b/src/mod_usertrack.c
index e24672f3..028a87c3 100644
--- a/src/mod_usertrack.c
+++ b/src/mod_usertrack.c
@@ -4,6 +4,7 @@
 #include "log.h"
 #include "buffer.h"
 #include "rand.h"
+#include "response.h"
 
 #include "plugin.h"
 
@@ -182,6 +183,7 @@ static int mod_usertrack_patch_connection(server *srv, connection *con, plugin_d
 
 URIHANDLER_FUNC(mod_usertrack_uri_handler) {
 	plugin_data *p = p_d;
+	buffer *cookie;
 	data_string *ds;
 	unsigned char h[16];
 	li_MD5_CTX Md5Ctx;
@@ -219,12 +221,9 @@ URIHANDLER_FUNC(mod_usertrack_uri_handler) {
 	}
 
 	/* set a cookie */
-	if (NULL == (ds = (data_string *)array_get_unused_element(con->response.headers, TYPE_STRING))) {
-		ds = data_response_init();
-	}
-	buffer_copy_string_len(ds->key, CONST_STR_LEN("Set-Cookie"));
-	buffer_copy_buffer(ds->value, p->conf.cookie_name);
-	buffer_append_string_len(ds->value, CONST_STR_LEN("="));
+	cookie = srv->tmp_buf;
+	buffer_copy_buffer(cookie, p->conf.cookie_name);
+	buffer_append_string_len(cookie, CONST_STR_LEN("="));
 
 
 	/* taken from mod_auth.c */
@@ -241,29 +240,29 @@ URIHANDLER_FUNC(mod_usertrack_uri_handler) {
 
 	li_MD5_Final(h, &Md5Ctx);
 
-	buffer_append_string_encoded_hex_lc(ds->value, (char *)h, 16);
+	buffer_append_string_encoded_hex_lc(cookie, (char *)h, 16);
 
 	/* usertrack.cookie-attrs, if set, replaces all other attrs */
 	if (!buffer_string_is_empty(p->conf.cookie_attrs)) {
-		buffer_append_string_buffer(ds->value, p->conf.cookie_attrs);
-		array_insert_unique(con->response.headers, (data_unset *)ds);
+		buffer_append_string_buffer(cookie, p->conf.cookie_attrs);
+		response_header_insert(srv, con, CONST_STR_LEN("Set-Cookie"), CONST_BUF_LEN(cookie));
 		return HANDLER_GO_ON;
 	}
 
-	buffer_append_string_len(ds->value, CONST_STR_LEN("; Path=/"));
-	buffer_append_string_len(ds->value, CONST_STR_LEN("; Version=1"));
+	buffer_append_string_len(cookie, CONST_STR_LEN("; Path=/"));
+	buffer_append_string_len(cookie, CONST_STR_LEN("; Version=1"));
 
 	if (!buffer_string_is_empty(p->conf.cookie_domain)) {
-		buffer_append_string_len(ds->value, CONST_STR_LEN("; Domain="));
-		buffer_append_string_encoded(ds->value, CONST_BUF_LEN(p->conf.cookie_domain), ENCODING_REL_URI);
+		buffer_append_string_len(cookie, CONST_STR_LEN("; Domain="));
+		buffer_append_string_encoded(cookie, CONST_BUF_LEN(p->conf.cookie_domain), ENCODING_REL_URI);
 	}
 
 	if (p->conf.cookie_max_age) {
-		buffer_append_string_len(ds->value, CONST_STR_LEN("; max-age="));
-		buffer_append_int(ds->value, p->conf.cookie_max_age);
+		buffer_append_string_len(cookie, CONST_STR_LEN("; max-age="));
+		buffer_append_int(cookie, p->conf.cookie_max_age);
 	}
 
-	array_insert_unique(con->response.headers, (data_unset *)ds);
+	response_header_insert(srv, con, CONST_STR_LEN("Set-Cookie"), CONST_BUF_LEN(cookie));
 
 	return HANDLER_GO_ON;
 }
diff --git a/src/mod_wstunnel.c b/src/mod_wstunnel.c
index cff378a6..3f959e18 100644
--- a/src/mod_wstunnel.c
+++ b/src/mod_wstunnel.c
@@ -759,8 +759,7 @@ static int create_MD5_sum(connection *con) {
 
 static int create_response_ietf_00(handler_ctx *hctx) {
     connection *con = hctx->gw.remote_conn;
-    array * const hdrs = con->response.headers;
-    data_string *ds;
+    buffer *value = hctx->srv->tmp_buf;
 
     /* "Origin" header is preferred
      * ("Sec-WebSocket-Origin" is from older drafts of websocket spec) */
@@ -803,16 +802,13 @@ static int create_response_ietf_00(handler_ctx *hctx) {
                               CONST_BUF_LEN(origin->value));
   #endif
 
-    ds = (data_string *)array_get_unused_element(hdrs, TYPE_STRING);
-    if (NULL == ds) ds = data_string_init();
-    buffer_copy_string_len(ds->key, CONST_STR_LEN("Sec-WebSocket-Location"));
     if (buffer_is_equal_string(con->uri.scheme, CONST_STR_LEN("https")))
-        buffer_copy_string_len(ds->value, CONST_STR_LEN("wss://"));
+        buffer_copy_string_len(value, CONST_STR_LEN("wss://"));
     else
-        buffer_copy_string_len(ds->value, CONST_STR_LEN("ws://"));
-    buffer_append_string_buffer(ds->value, con->request.http_host);
-    buffer_append_string_buffer(ds->value, con->uri.path);
-    array_insert_unique(hdrs, (data_unset *)ds);
+        buffer_copy_string_len(value, CONST_STR_LEN("ws://"));
+    buffer_append_string_buffer(value, con->request.http_host);
+    buffer_append_string_buffer(value, con->uri.path);
+    response_header_insert(hctx->srv, con, CONST_STR_LEN("Sec-WebSocket-Location"), CONST_BUF_LEN(value));
 
     return 0;
 }
@@ -827,6 +823,7 @@ static int create_response_ietf_00(handler_ctx *hctx) {
 
 static int create_response_rfc_6455(handler_ctx *hctx) {
     connection *con = hctx->gw.remote_conn;
+    buffer *value = hctx->srv->tmp_buf;
     array * const hdrs = con->response.headers;
     data_string *ds;
     SHA_CTX sha;
@@ -856,11 +853,9 @@ static int create_response_rfc_6455(handler_ctx *hctx) {
                            CONST_STR_LEN("upgrade"));
   #endif
 
-    ds = (data_string *)array_get_unused_element(hdrs, TYPE_STRING);
-    if (NULL == ds) ds = data_string_init();
-    buffer_copy_string_len(ds->key, CONST_STR_LEN("Sec-WebSocket-Accept"));
-    buffer_append_base64_encode(ds->value, sha_digest, SHA_DIGEST_LENGTH, BASE64_STANDARD);
-    array_insert_unique(hdrs, (data_unset *)ds);
+    buffer_string_set_length(value, 0);
+    buffer_append_base64_encode(value, sha_digest, SHA_DIGEST_LENGTH, BASE64_STANDARD);
+    response_header_insert(hctx->srv, con, CONST_STR_LEN("Sec-WebSocket-Accept"), CONST_BUF_LEN(value));
 
     if (hctx->frame.type == MOD_WEBSOCKET_FRAME_TYPE_BIN)
         array_set_key_value(hdrs, CONST_STR_LEN("Sec-WebSocket-Protocol"),