Hi Serge,

What Pharo version are you on? What is your `file` object? If `file` is a FileReference, you need to know that by default, using `readStream` provides now an encoded file (to keep backwards compatibility with what most users were doing until now).

And I think that GZip should just decode/decompress binary data.

Instead of asking it for a readStream, try asking for a `binaryReadStream`.

compressed := file binaryReadStream.

stream := (GZipReadStream on: compressed) upToEnd asByteArray readStream.