Learner1D.ask breaks when adding points in some order

l = adaptive.Learner1D(lambda x: x, (0, 1))
l.tell_many([1, 0, 0.5], [0, 0, 0])
l.ask(1)

Traceback

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-17-1b520d635f37> in <module>()
      2 l = adaptive.Learner1D(lambda x: x, (0, 1))
      3 l.tell_many([1, 0, 0.5], [0, 0, 0])
----> 4 l.ask(1)

~/Work/adaptive/adaptive/learner/learner1D.py in ask(self, n, add_data)
    301                      in self.neighbors.items()][:-1]
    302 
--> 303         for x_left, x_right in intervals:
    304             self.losses[x_left, x_right] = (
    305                 self.loss_per_interval((x_left, x_right), self._scale, self.data)

~/Work/adaptive/adaptive/learner/base_learner.py in tell_many(self, xs, ys)
     43         """
     44         for x, y in zip(xs, ys):
---> 45             self.tell(x, y)
     46 
     47     @abc.abstractmethod

~/Work/adaptive/adaptive/learner/learner1D.py in tell(self, x, y)
    239         self.update_scale(x, y)
    240 
--> 241         # Update the losses
    242         self.update_losses(x, real)
    243 

~/Work/adaptive/adaptive/learner/learner1D.py in update_losses(self, x, real)
    159             a, b = self.find_neighbors(x, self.neighbors_combined)
    160             if x_left is not None and x_right is not None:
--> 161                 dx = x_right - x_left
    162                 loss = self.losses[x_left, x_right]
    163                 losses_combined[a, x] = (x - a) * loss / dx

KeyError: (0, 1)