diff --git a/Machines/AtariST/Video.cpp b/Machines/AtariST/Video.cpp
index 58f071b10..984f3865d 100644
--- a/Machines/AtariST/Video.cpp
+++ b/Machines/AtariST/Video.cpp
@@ -26,7 +26,7 @@ struct VerticalParams {
 	const int reset_enable;
 	const int height;
 } vertical_params[3] = {
-	{63, 264, 313},	// 47 rather than 63 on early machines.
+	{63, 263, 313},	// 47 rather than 63 on early machines.
 	{34, 234, 263},
 	{1, 401, 500}	// 72 Hz mode: who knows?
 };