diff --git a/src/lib/rfc3161.c b/src/lib/rfc3161.c
index bdec0d6..520cc4d 100644
--- a/src/lib/rfc3161.c
+++ b/src/lib/rfc3161.c
@@ -79,7 +79,7 @@ static int begin_request_handler(struct mg_connection *conn) {
     // Send HTTP reply to the client
     mg_printf(conn,
               "HTTP/1.1 200 OK\r\n"
-              "Content-Type: text/plain\r\n"
+              "Content-Type: application/timestamp-reply\r\n"
               "Content-Length: %d\r\n" // Always set Content-Length
               "\r\n"
               "%s",