diff --git a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/TIA.cs b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/TIA.cs
index d95eba6713..a7015e6760 100644
--- a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/TIA.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/TIA.cs
@@ -923,7 +923,7 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 		{
 			var maskedAddr = (ushort)(addr & 0x000F);
 			byte coll = 0;
-			int mask = 0;
+			int mask = 0xFF;
 
 			if (maskedAddr == 0x00) // CXM0P
 			{