diff --git a/src/lib/connection.c b/src/lib/connection.c
index f2d54efcaa..1a5d6b8bd4 100644
--- a/src/lib/connection.c
+++ b/src/lib/connection.c
@@ -165,6 +165,16 @@ static void connection_init_streams(struct connection *conn)
 	}
 }
 
+void connection_streams_changed(struct connection *conn)
+{
+	const struct connection_settings *set = &conn->list->set;
+
+	if (set->input_max_size != 0 && conn->io != NULL) {
+		io_remove(&conn->io);
+		conn->io = io_add_istream(conn->input, *conn->list->v.input, conn);
+	}
+}
+
 static void connection_client_connected(struct connection *conn, bool success)
 {
 	i_assert(conn->list->set.client);
diff --git a/src/lib/connection.h b/src/lib/connection.h
index 70dc2f24a5..bdfde1d81a 100644
--- a/src/lib/connection.h
+++ b/src/lib/connection.h
@@ -129,6 +129,8 @@ int connection_client_connect(struct connection *conn);
 void connection_disconnect(struct connection *conn);
 void connection_deinit(struct connection *conn);
 
+void connection_streams_changed(struct connection *conn);
+
 /* Returns -1 = disconnected, 0 = nothing new, 1 = something new.
    If input_full_behavior is ALLOW, may return also -2 = buffer full. */
 int connection_input_read(struct connection *conn);