diff --git a/src/burn/drv/sega/d_sys18.cpp b/src/burn/drv/sega/d_sys18.cpp
index 3acb19abea..d26dae4f88 100644
--- a/src/burn/drv/sega/d_sys18.cpp
+++ b/src/burn/drv/sega/d_sys18.cpp
@@ -1,4 +1,5 @@
 #include "sys16.h"
+#include <math.h> // round()
 
 /*====================================================
 Input defs