--- toonz/sources/include/tcg/poly_ops.h	2021-12-14 00:11:14.717028000 +0300
+++ toonz/sources/include/tcg/poly_ops.h	2021-12-14 00:11:39.304315000 +0300
@@ -5,6 +5,7 @@
 
 // tcg includes
 #include "macros.h"
+#include <algorithm>
 
 /*!
   \file     tcg_poly_ops.h
