diff --git a/purple-websocket.c b/purple-websocket.c
index 55eb371..0554766 100644
--- a/purple-websocket.c
+++ b/purple-websocket.c
@@ -463,7 +463,7 @@ static void ws_connect_cb(gpointer data, gint source, const gchar *error_message
 }
 
 PurpleWebsocket *purple_websocket_connect(PurpleAccount *account,
-		const char *url, const char *protocol,
+		const char *url, const char *protocol, const char *cookies,
 		PurpleWebsocketCallback callback, void *user_data) {
 	gboolean ssl = FALSE;
 
@@ -515,6 +515,8 @@ Sec-WebSocket-Key: %s\r\n\
 Sec-WebSocket-Version: 13\r\n", path, host, ws->key);
 		if (protocol)
 			g_string_append_printf(request, "Sec-WebSocket-Protocol: %s\r\n", protocol);
+		if (cookies)
+			g_string_append_printf(request, "Cookie: %s\r\n", cookies);
 		g_string_append(request, "\r\n");
 
 		ws->output.len = request->len;
diff --git a/purple-websocket.h b/purple-websocket.h
index 0416750..0f3eae0 100644
--- a/purple-websocket.h
+++ b/purple-websocket.h
@@ -17,7 +17,7 @@ typedef enum _PurpleWebsocketOp {
 
 typedef void (*PurpleWebsocketCallback)(PurpleWebsocket *ws, gpointer user_data, PurpleWebsocketOp op, const guchar *msg, size_t len);
 
-PurpleWebsocket *purple_websocket_connect(PurpleAccount *account, const char *url, const char *protocol, PurpleWebsocketCallback callback, void *user_data);
+PurpleWebsocket *purple_websocket_connect(PurpleAccount *account, const char *url, const char *protocol, const char *cookies, PurpleWebsocketCallback callback, void *user_data);
 void purple_websocket_send(PurpleWebsocket *ws, PurpleWebsocketOp op, const guchar *msg, size_t len);
 void purple_websocket_abort(PurpleWebsocket *ws);
 
diff --git a/slack-rtm.c b/slack-rtm.c
index d4ee8f2..e32216e 100644
--- a/slack-rtm.c
+++ b/slack-rtm.c
@@ -187,8 +187,15 @@ static gboolean rtm_connect_cb(SlackAccount *sa, gpointer data, json_value *json
 	slack_blist_init(sa);
 
 	slack_login_step(sa);
+
+	gchar *cookie = NULL;
+	if (sa->d_cookie)
+		cookie = g_strconcat("d=", sa->d_cookie, NULL);
+
 	purple_debug_info("slack", "RTM URL: %s\n", url);
-	sa->rtm = purple_websocket_connect(sa->account, url, NULL, rtm_cb, sa);
+	sa->rtm = purple_websocket_connect(sa->account, url, NULL, cookie, rtm_cb, sa);
+
+	g_free(cookie);
 
 	sa->ping_timer = purple_timeout_add_seconds(60, ping_timer, sa);
 	return FALSE;