Append large string to document

I am using java API for couchbase .
I am concatinating string using append method .

It seems that the append operation succeded , I got ‘true’ from the OperationFuture result of the append operation how ever when i am retrieving the document again it seems that the last appended string was not added.
This issue occurs when the appended string exceed the transcoder max treshold for compressing the string.
If I am appending a shorter string it seems that the append operation was successful.

Is there something I am missing ?