diff --git a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/SxROM.cs b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/SxROM.cs
index 53e685ee3b..8bb570b00b 100644
--- a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/SxROM.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/SxROM.cs
@@ -427,6 +427,14 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			prg_mask = (Cart.prg_size / 16) - 1;
 			vram_mask = (Cart.vram_size*1024) - 1;
 			chr_mask = (Cart.chr_size / 8 * 2) - 1;
+			//Chip n Dale (PC10) has a nonstandard chr size, which makes the mask nonsense
+			// let's put in a special case to deal with it
+			if (Cart.chr_size==136)
+			{
+				chr_mask = (128 / 8 * 2) - 1;
+			}
+
+
 			if (!disablemirror)
 				SetMirrorType(mmc1.mirror);
 			ppuclock = pputimeout;