diff --git a/bin/dither/dither.rb b/bin/dither/dither.rb
index eec3786..d4024e3 100644
--- a/bin/dither/dither.rb
+++ b/bin/dither/dither.rb
@@ -6,7 +6,7 @@ MiniMagick.logger.level = Logger::DEBUG
 ROOT = ENV.fetch("ROOT")
 KEY = ENV.fetch("KEY")
 DITHER = ENV["DITHER"] != "0"
-FORMAT = DITHER ? "png" : "webp"
+FORMAT = "png"
 
 get "/*" do |path|
   halt 404, {"Content-Type" => "text/plain"}, "not found" unless File.exist?("#{ROOT}/#{path}.enc")