Hi guys. I found that GZipWriteStream throws an error when closing it twice. Example: | aStream zipStream | aStream := ByteArray new writeStream binary. zipStream := GZipWriteStream on: aStream. zipStream close. zipStream close. All the streams I know do not throw an error in that case. And moreoever, it gets things complicated when using #on:do:. For example: FileStream forceNewFileNamed: testFileName do: [ :stream | GZipWriteStream on: stream binary do: [ :gzipStream | FLSerializer newDefault serialize: anObject on: gzipStream ] ]. In thise case, FLSerializer closes the stream at the end. No matter whether Fuel should do that or not, the thing is that in this I have the mentioned problem. So...my question is, is this a bug? if it is, do you have a better idea that changing #close to this: ZipWriteStream >> close literals isNil ifTrue: [ "#initialize sets this instVar to a specific value. #release puts it in nil, and #release is called from #flushBlock: which is called from #close:. Therefore, if it is nil, it means the stream has already been closed. If we try to close it twice, #flushBlock will throw an error because its instance variables are with nil" ^ self] self deflateBlock. self flushBlock: true. encoder close. -- Mariano http://marianopeck.wordpress.com