diff --git a/heat.cpp b/heat.cpp
index caf7817..e75f1f6 100644
--- a/heat.cpp
+++ b/heat.cpp
@@ -44,6 +44,7 @@ void Heat::generate(const std::string& filename, const pCaches& points, int stam
 	Magick::Image contour(MAPS_DIR / mp->map_file);
 	Magick::Image heatmap(mp->size_x, mp->size_y, "RGBA", Magick::CharPixel, &image[0]);
 
+	contour.type(Magick::TrueColorType);
 	contour.composite(heatmap, 0, 0, Magick::OverCompositeOp);
 	contour.write(filename);
 	// heatmap.write("geostat_heat.png");