diff --git a/BizHawk.Emulation/BizHawk.Emulation.csproj b/BizHawk.Emulation/BizHawk.Emulation.csproj
index 6f07a67f88..3468181ce8 100644
--- a/BizHawk.Emulation/BizHawk.Emulation.csproj
+++ b/BizHawk.Emulation/BizHawk.Emulation.csproj
@@ -286,6 +286,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\Mapper197.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\Mapper205.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\Mapper245.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\Mapper250.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\MMC3.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\NES-QJ.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\TQROM.cs" />
diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/MMC3_family/Mapper250.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/MMC3_family/Mapper250.cs
new file mode 100644
index 0000000000..e27b342fff
--- /dev/null
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/MMC3_family/Mapper250.cs
@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BizHawk.Emulation.Consoles.Nintendo
+{
+	// Time Diver Avenger (Unl)
+	// MMC3 with slightly different write scheme
+	// presumably the board contains an MMC3 clone with some unique edge case behavior; unknown
+	public class Mapper250 : MMC3Board_Base
+	{
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			switch (Cart.board_type)
+			{
+				case "MAPPER250":
+					break;
+				default:
+					return false;
+			}
+			BaseSetup();
+			return true;
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			base.WritePRG(addr & 0x6000 | addr >> 10 & 1, (byte)(addr & 0xff));
+		}
+	}
+}