diff --git a/GPU/Software/Rasterizer.cpp b/GPU/Software/Rasterizer.cpp
index 2a1ca59d42..7f2820b0ac 100644
--- a/GPU/Software/Rasterizer.cpp
+++ b/GPU/Software/Rasterizer.cpp
@@ -830,14 +830,13 @@ static inline Vec3<int> GetSourceFactor(const Vec4<int>& source, const Vec4<int>
 		return Vec3<int>::AssignToAll(2 * source.a());
 
 	case GE_SRCBLEND_DOUBLEINVSRCALPHA:
-		return Vec3<int>::AssignToAll(255 - 2 * source.a());
+		return Vec3<int>::AssignToAll(255 - std::min(2 * source.a(), 255));
 
 	case GE_SRCBLEND_DOUBLEDSTALPHA:
 		return Vec3<int>::AssignToAll(2 * dst.a());
 
 	case GE_SRCBLEND_DOUBLEINVDSTALPHA:
-		// TODO: Clamping?
-		return Vec3<int>::AssignToAll(255 - 2 * dst.a());
+		return Vec3<int>::AssignToAll(255 - std::min(2 * dst.a(), 255));
 
 	case GE_SRCBLEND_FIXA:
 	default:
@@ -879,13 +878,13 @@ static inline Vec3<int> GetDestFactor(const Vec4<int>& source, const Vec4<int>&
 		return Vec3<int>::AssignToAll(2 * source.a());
 
 	case GE_DSTBLEND_DOUBLEINVSRCALPHA:
-		return Vec3<int>::AssignToAll(255 - 2 * source.a());
+		return Vec3<int>::AssignToAll(255 - std::min(2 * source.a(), 255));
 
 	case GE_DSTBLEND_DOUBLEDSTALPHA:
 		return Vec3<int>::AssignToAll(2 * dst.a());
 
 	case GE_DSTBLEND_DOUBLEINVDSTALPHA:
-		return Vec3<int>::AssignToAll(255 - 2 * dst.a());
+		return Vec3<int>::AssignToAll(255 - std::min(2 * dst.a(), 255));
 
 	case GE_DSTBLEND_FIXB:
 	default:
@@ -896,6 +895,7 @@ static inline Vec3<int> GetDestFactor(const Vec4<int>& source, const Vec4<int>&
 
 static inline Vec3<int> AlphaBlendingResult(const Vec4<int> &source, const Vec4<int> &dst)
 {
+	// Note: These factors cannot go below 0, but they can go above 255 when doubling.
 	Vec3<int> srcfactor = GetSourceFactor(source, dst);
 	Vec3<int> dstfactor = GetDestFactor(source, dst);