diff --git a/lib/builder-utils.sh b/lib/builder-utils.sh
index 8b9b5cf..700414b 100644
--- a/lib/builder-utils.sh
+++ b/lib/builder-utils.sh
@@ -188,7 +188,7 @@ convert_image() {
 	$OUTPUT_DIR/removed_black.png
 
     # create the matte
-    convert $OUTPUT_DIR/removed_black.png -channel matte -separate  +matte \
+    convert $OUTPUT_DIR/removed_black.png -channel matte -negate -separate +matte \
 	$OUTPUT_DIR/matte.png
 
     # negate the colors