Hmm, the actual version of file-storage is 5.10.0d14, so d13 seems pretty new. Is this a new install, or have you updated your packages to a recent version?
I can't reproduce the problem on a fresh instance, "folder-chunk.tcl" sets the variable via an include_contract... so it should be set in this file. Can you provide some more details?
Have you fixed the your earlier problem with the filehandle?
