[Pharo-dev] FileSystem memory bug?

Hi, I'm working in latest Pharo (30577) with STON (bleeding edge) and I get MNU:SmallInteger>>isSeparator when I evaluate the code below. Is my code wrong? The idea is to make my test suite work in the memory file system. | fileSystem | fileSystem := FileSystem memory. (fileSystem / 'file.txt') ensureCreateFile. STON writer on: (fileSystem / 'file.txt') writeStream; nextPut: 'hi'. STON reader on: (fileSystem / 'file.txt') readStream; next. Thanks in advance. Martín