[plt-scheme] (lib "sandbox.ss") broke the contract

hello,

i tried to create a sandboxed evaluator from a module definition
with a 'prefix' require clause, and ran into the following error.

groetjes,
tom


Welcome to MzScheme v371 [3m], Copyright (c) 2004-2007 PLT Scheme Inc.

(require (lib "sandbox.ss"))
(make-evaluator '(module pawfaliki mzscheme
                   (require (lib "yacc.ss" "parser-tools")
                            (lib "lex.ss" "parser-tools")
                            (prefix : (lib "lex-sre.ss" "parser-tools")))
                   #f))


(lib "sandbox.ss") broke the contract 
  (->
   module-path-v?
   (or/c (-> path-string?) path-string? false/c)
   path?)
on resolve-module-path; expected <module-path-v?>, given: (prefix : (lib "lex-sre.ss" "parser-tools"))

 === context ===
/usr/local/plt/collects/mzlib/private/contract-guts.ss:196:2: raise-contract-error
resolve-module-path
/usr/local/plt/collects/mzlib/sandbox.ss:150:34
/usr/local/plt/collects/mzlib/sandbox.ss:144:2: module-specs->non-lib-paths
/usr/local/plt/collects/mzlib/sandbox.ss:128:2: module-specs->path-permissions
/usr/local/plt/collects/mzlib/sandbox.ss:518:4: make-evaluator