get error

test.lua

#!/usr/bin/env tarantool

box.cfg{ logger = '/dev/null' }

local test = require('tap').test()

test:plan(3)


box.schema.space.create(
    'test',
    {
        engine          = 'memtx',
        format          = { { name = 'id' }, { name = 'domain' }, { name = 'path' } },
        if_not_exists   = true
    }
)

box.space.test:create_index(
    'pk',
    {
        unique          = true,
        type            = 'hash',
        parts           = { 1, 'str' },
        if_not_exists   = true,
    }
)

box.space.test:create_index(
    'pti',
    {
        unique          = false,
        type            = 'tree',
        parts           = { 3, 'str', 2, 'str', 1, 'str' },
        if_not_exists   = true,
    }
)


box.space.test:truncate()

box.space.test:insert{'first', '', '/path/to'}

local tuples = box.space.test.index.pk:select({ 'first' }, { iterator = 'EQ' })
test:is(#tuples, 1, 'one tuple in database')

tuples = box.space.test.index.pti:select{ '/path/to', '', 'first' }
test:is(#tuples, 1, 'one tuple selected by secondary index')


local tuple = box.space.test.index.pti:get{ '/path/to', '', 'first' }
test:ok(tuple, 'tuple was selected by :get')
os.exit(test:check() == true and 0 or -1)

raise error:

2016-10-05 16:48:37.030 [27458] test.lua F> More than one tuple found by get()