Problem feeding indicators through each other

[CooleRnax]

When I setup init this way I get nan in bears_change (direction change) indicator.

bears = BearsPower(self.data, period=15)
bears_change = Change(bears)

But when I do it ugly way everything works, where is the problem?

bears = BearsPower(self.data, period=15)
bears_change = Change(bears.power)

Indicators code:

class Move(Indicator):
    lines = ('move',)

    def __init__(self):
        self.lines.move = self.data - self.data(-1)
        super(Move, self).__init__()


class Change(Indicator):
    lines = ('change',)

    def __init__(self):
        self.move = Move(self.data)
        super(Change, self).__init__()

    def next(self):
        change = 0
        if self.move[-1] < 0 and self.move[0] > 0:
            change += 1
        elif self.move[-1] > 0 and self.move[0] < 0:
            change -= 1
        self.lines.change[0] = change

class BearsPower(Indicator):
    lines = ('power',)
    params = dict(
        period=13,
        mode='close',
    )

    def __init__(self):
        if self.p.mode == 'close':
            source = self.data.close
        elif self.p.mode == 'high':
            source = self.data.high
        elif self.p.mode == 'low':
            source = self.data.low

        self.ema = EMA(source, period=self.p.period)
        self.lines.power = self.data.low - self.ema
        super(BearsPower, self).__init__()