diff --git a/trunk/src/boards/mmc5.cpp b/trunk/src/boards/mmc5.cpp
index 1a4e870c..a9789c45 100644
--- a/trunk/src/boards/mmc5.cpp
+++ b/trunk/src/boards/mmc5.cpp
@@ -512,21 +512,40 @@ void MMC5Synco(void) {
 }
 
 void MMC5_hb(int scanline) {
-	if (scanline == 240) {
+	//zero 24-jul-2014 - revised for newer understanding, to fix metal slader glory credits. see r7371 in bizhawk
+	
+	int sl = scanline + 1;
+	int ppuon = (PPU[1] & 0x18);
+
+	if (!ppuon || sl >= 241)
+	{
+		// whenever rendering is off for any reason (vblank or forced disable
+		// the irq counter resets, as well as the inframe flag (easily verifiable from software)
+		MMC5IRQR &= ~0x40;
+		MMC5IRQR &= ~0x80;
 		MMC5LineCounter = 0;
-		MMC5IRQR = 0x40;
+		X6502_IRQEnd(FCEU_IQEXT);
 		return;
 	}
-	if (MMC5LineCounter < 240) {
-		if (MMC5LineCounter == IRQScanline) {
+
+	if (!(MMC5IRQR&0x40))
+	{
+		MMC5IRQR |= 0x40;
+		MMC5IRQR &= ~0x80;
+		MMC5LineCounter = 0;
+		X6502_IRQEnd(FCEU_IQEXT);
+	}
+	else
+	{
+		MMC5LineCounter++;
+		if (MMC5LineCounter == IRQScanline)
+		{
 			MMC5IRQR |= 0x80;
 			if (IRQEnable & 0x80)
 				X6502_IRQBegin(FCEU_IQEXT);
 		}
-		MMC5LineCounter++;
 	}
-	if (MMC5LineCounter == 240)
-		MMC5IRQR = 0;
+
 }
 
 void MMC5_StateRestore(int version) {
diff --git a/trunk/src/ppu.cpp b/trunk/src/ppu.cpp
index 168e26fd..13414730 100644
--- a/trunk/src/ppu.cpp
+++ b/trunk/src/ppu.cpp
@@ -1221,7 +1221,7 @@ static void DoLine(void) {
 	int x;
 	uint8 *target = XBuf + (scanline << 8);
 
-	if (MMC5Hack && (ScreenON || SpriteON)) MMC5_hb(scanline);
+	if (MMC5Hack) MMC5_hb(scanline);
 
 	X6502_Run(256);
 	EndRL();
@@ -1790,7 +1790,7 @@ int FCEUPPU_Loop(int skip) {
 				DEBUG(FCEUD_UpdatePPUView(scanline, 1));
 				DoLine();
 			}
-			if (MMC5Hack && (ScreenON || SpriteON)) MMC5_hb(scanline);
+			if (MMC5Hack) MMC5_hb(scanline);
 			for (x = 1, max = 0, maxref = 0; x < 7; x++) {
 				if (deempcnt[x] > max) {
 					max = deempcnt[x];
@@ -2033,7 +2033,7 @@ int FCEUX_PPU_Loop(int skip) {
 				DEBUG(FCEUD_UpdateNTView(scanline = yp, 1));
 			}
 
-			if (sl != 0) if (MMC5Hack && PPUON) MMC5_hb(yp);
+			if (MMC5Hack) MMC5_hb(yp);
 
 
 			//twiddle the oam buffers
@@ -2303,7 +2303,7 @@ int FCEUX_PPU_Loop(int skip) {
 				runppu(1);
 		}	//scanline loop
 
-		if (MMC5Hack && PPUON) MMC5_hb(240);
+		if (MMC5Hack) MMC5_hb(240);
 
 		//idle for one line
 		runppu(kLineTime);