--- a/Makefile~	2020-04-22 23:07:33.000000000 +0200
+++ b/Makefile	2020-04-22 23:11:46.356767595 +0200
@@ -194,7 +194,7 @@
 ifdef MISSING_ZOPFLI
 	@$(OPTIPNG) -quiet -o7 -clobber -force -out "$@" "$<"
 else
-	@$(ZOPFLIPNG) -y "$<" "$@" 1> /dev/null 2>&1
+	@$(ZOPFLIPNG) -y "$<" "$@" 2>&1
 endif