diff --git a/3rdparty/nvtt/nvtt.cpp b/3rdparty/nvtt/nvtt.cpp
index aa1c2d2..0cc0df4 100644
--- a/3rdparty/nvtt/nvtt.cpp
+++ b/3rdparty/nvtt/nvtt.cpp
@@ -50,9 +50,9 @@ namespace nvtt
 					for (uint32_t blockX = 0; blockX < ZOH::Tile::TILE_W; ++blockX)
 					{
 						nv::Vector4 color = srcRgba[blockY*srcRgbaStride + blockX];
-						zohTile.data[blockY][blockX].x = float(int16_t(bx::halfFromFloat(color.x) ) );
-						zohTile.data[blockY][blockX].y = float(int16_t(bx::halfFromFloat(color.y) ) );
-						zohTile.data[blockY][blockX].z = float(int16_t(bx::halfFromFloat(color.z) ) );
+						zohTile.data[blockY][blockX].x = float(int16_t(bx::halfFromFloat(bx::max(color.x, 0.0f) ) ) );
+						zohTile.data[blockY][blockX].y = float(int16_t(bx::halfFromFloat(bx::max(color.y, 0.0f) ) ) );
+						zohTile.data[blockY][blockX].z = float(int16_t(bx::halfFromFloat(bx::max(color.z, 0.0f) ) ) );
 					}
 				}