diff --git a/GPU/Software/Rasterizer.cpp b/GPU/Software/Rasterizer.cpp
index b856ba7b8e..051bef282b 100644
--- a/GPU/Software/Rasterizer.cpp
+++ b/GPU/Software/Rasterizer.cpp
@@ -1512,39 +1512,35 @@ void ClearRectangle(const VertexData &v0, const VertexData &v1)
 		}
 	}
 
-	const u32 new_color = v1.color0.ToRGBA();
-	u16 new_color16;
-
 	// Note: this stays 0xFFFFFFFF if keeping color and alpha, even for 16-bit.
 	u32 keepOldMask = 0xFFFFFFFF;
+	if (gstate.isClearModeColorMask())
+		keepOldMask &= 0xFF000000;
+	if (gstate.isClearModeAlphaMask())
+		keepOldMask &= 0x00FFFFFF;
+
+	// The pixel write masks are respected in clear mode.
+	keepOldMask |= gstate.getColorMask();
+
+	const u32 new_color = v1.color0.ToRGBA();
+	u16 new_color16;
 	switch (gstate.FrameBufFormat()) {
 	case GE_FORMAT_565:
 		new_color16 = RGBA8888ToRGB565(new_color);
-		if (gstate.isClearModeColorMask())
-			keepOldMask = 0;
+		keepOldMask = keepOldMask == 0 ? 0 : (0xFFFF0000 | RGBA8888ToRGB565(keepOldMask));
 		break;
 
 	case GE_FORMAT_5551:
 		new_color16 = RGBA8888ToRGBA5551(new_color);
-		if (gstate.isClearModeColorMask())
-			keepOldMask &= 0x00008000;
-		if (gstate.isClearModeAlphaMask())
-			keepOldMask &= 0x00007FFF;
+		keepOldMask = keepOldMask == 0 ? 0 : (0xFFFF0000 | RGBA8888ToRGBA5551(keepOldMask));
 		break;
 
 	case GE_FORMAT_4444:
 		new_color16 = RGBA8888ToRGBA4444(new_color);
-		if (gstate.isClearModeColorMask())
-			keepOldMask &= 0x0000F000;
-		if (gstate.isClearModeAlphaMask())
-			keepOldMask &= 0x00000FFF;
+		keepOldMask = keepOldMask == 0 ? 0 : (0xFFFF0000 | RGBA8888ToRGBA4444(keepOldMask));
 		break;
 
 	case GE_FORMAT_8888:
-		if (gstate.isClearModeColorMask())
-			keepOldMask &= 0xFF000000;
-		if (gstate.isClearModeAlphaMask())
-			keepOldMask &= 0x00FFFFFF;
 		break;
 
 	case GE_FORMAT_INVALID:
@@ -1552,9 +1548,6 @@ void ClearRectangle(const VertexData &v0, const VertexData &v1)
 		break;
 	}
 
-	// The pixel write masks are respected in clear mode.
-	keepOldMask |= gstate.getColorMask();
-
 	if (keepOldMask == 0) {
 		ScreenCoords pprime(minX, minY, 0);
 		const int stride = gstate.FrameBufStride();