From 7ff08fb63e4f96cb55ba4c481d59c2dc0a6fbde9 Mon Sep 17 00:00:00 2001
From: alyosha-tas <alexei.f.k@gmail.com>
Date: Tue, 26 Jun 2018 08:17:33 -0400
Subject: [PATCH] GBHawk: MBC2 proper Bank masking Fixes #1229

---
 .../Consoles/Nintendo/GBHawk/Mappers/Mapper_MBC2.cs           | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Mappers/Mapper_MBC2.cs b/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Mappers/Mapper_MBC2.cs
index dfda342323..7510d00522 100644
--- a/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Mappers/Mapper_MBC2.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Mappers/Mapper_MBC2.cs
@@ -4,7 +4,7 @@ using System;
 
 namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 {
-	// MBC1 with bank switching and RAM
+	// MBC2 with bank switching and RAM
 	public class MapperMBC2 : MapperBase
 	{
 		public int ROM_bank;
@@ -62,7 +62,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 			{
 				if ((addr & 0x100) > 0)
 				{
-					ROM_bank = value & 0xF;
+					ROM_bank = value & 0xF & ROM_mask;
 					if (ROM_bank==0) { ROM_bank = 1; }
 				}
 			}