error syntax on list FIELD_TYPES

I've got this error when I try to migrate:

[127.0.0.1] out:     __import__(name)
[127.0.0.1] out:   File "/usr/lib/python2.6/site-packages/xapian_backend.py", line 64
[127.0.0.1] out:     FIELD_TYPES = {'text', 'integer', 'date', 'datetime', 'float', 'boolean'}
[127.0.0.1] out:                          ^
[127.0.0.1] out: SyntaxError: invalid syntax