Bench init error

Traceback (most recent call last):
File “/usr/local/bin/bench”, line 9, in
load_entry_point(‘bench==0.1’, ‘console_scripts’, ‘bench’)()
File “/home/frappe/bench-repo/bench/cli.py”, line 56, in cli
bench()
File “/usr/local/lib/python2.7/dist-packages/click/core.py”, line 664, in call
return self.main(*args, **kwargs)
File “/usr/local/lib/python2.7/dist-packages/click/core.py”, line 644, in main
rv = self.invoke(ctx)
File “/usr/local/lib/python2.7/dist-packages/click/core.py”, line 991, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File “/usr/local/lib/python2.7/dist-packages/click/core.py”, line 837, in invoke
return ctx.invoke(self.callback, **ctx.params)
File “/usr/local/lib/python2.7/dist-packages/click/core.py”, line 464, in invoke
return callback(*args, **kwargs)
File “/home/frappe/bench-repo/bench/cli.py”, line 163, in init
frappe_branch=frappe_branch, reference_bench=reference)
File “/home/frappe/bench-repo/bench/utils.py”, line 66, in init
get_app(‘frappe’, frappe_path, branch=frappe_branch, bench=path, build_asset_files=False, reference_bench=reference_bench)
File “/home/frappe/bench-repo/bench/app.py”, line 52, in get_app
reference = os.path.abspath(os.path.join(reference_bench, ‘apps’, app))
File “/usr/lib/python2.7/posixpath.py”, line 77, in join
elif path == ‘’ or path.endswith(’/’):
AttributeError: ‘NoneType’ object has no attribute ‘endswith’

bench init frappe-bench --reference ‘’
that works