diff --git a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/PPU.cs b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/PPU.cs
index 16c986736f..74e0406d60 100644
--- a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/PPU.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/PPU.cs
@@ -119,7 +119,9 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 						goto loopout;
 
 					short s = xbuf[j * 256 + i];
-					sum += _currentLuma[s];
+					
+					if ((s & 0x8000)==0)
+						sum += _currentLuma[s];
 				}
 			}
 			loopout: