diff --git a/lib/rackup/stream.rb b/lib/rackup/stream.rb
index 137f8ca..29c97ac 100644
--- a/lib/rackup/stream.rb
+++ b/lib/rackup/stream.rb
@@ -30,7 +30,7 @@ module Reader
       # @param buffer [String] the buffer which will receive the data
       # @return a buffer containing the data
       def read(length = nil, buffer = nil)
-        return '' if length == 0
+        return buffer ? buffer.clear : String.new(encoding: Encoding::BINARY) if length == 0
 
         buffer ||= String.new.force_encoding(Encoding::BINARY)