diff --git a/ppu.cpp b/ppu.cpp
index 001a4a23..cf904b55 100644
--- a/ppu.cpp
+++ b/ppu.cpp
@@ -1566,7 +1566,8 @@ void S9xSetCPU (uint8 Byte, uint16 Address)
 					CPU.IRQTransition = FALSE;
 				}
 
-				S9xUpdateIRQPositions(false);
+				if ((Byte & 0x30) != (Memory.FillRAM[0x4200] & 0x30))
+					S9xUpdateIRQPositions(false);
 
 				// NMI can trigger immediately during VBlank as long as NMI_read ($4210) wasn't cleard.
 				if ((Byte & 0x80) && !(Memory.FillRAM[0x4200] & 0x80) &&