diff --git a/src/box/iproto_port.cc b/src/box/iproto_port.cc
index 0624adce98957a840b1eeb37e69842e3393d0edd..06110d6b8bcce5bbd6cadff0d27bf62f235fe2e4 100644
--- a/src/box/iproto_port.cc
+++ b/src/box/iproto_port.cc
@@ -148,10 +148,11 @@ static inline void
 iproto_port_add_tuple(struct port *ptr, struct tuple *tuple)
 {
 	struct iproto_port *port = iproto_port(ptr);
-	if (++port->found == 1) {
+	if (port->found == 0) {
 		/* Found the first tuple, add header. */
 		port->svp = iproto_prepare_select(port->buf);
 	}
+	port->found++;
 	tuple_to_obuf(tuple, port->buf);
 }