Not all data are displayed by bar graph with chaco

Question

With creating simple bar plot with chaco strange behavior is occured: half of plot is filled with line_color, another one with fill_color and the last one is not drawn at all (view screenshot). It is expected that data from 0 to 7000 for x and from 0 to 150 for y should be displayed and filled with line_color. With using small values it works fine (for example using 50 instead of 150 for y values). Is there an explanation of such behavior? How it can be solved?

Code below demonstrates the problem:

from enable.api import ComponentEditor
from traits.api import Instance, HasStrictTraits
from traitsui.api import View, UItem
from chaco.api import Plot, ArrayPlotData


class TestPlot(HasStrictTraits):
    plot = Instance(Plot)
    traits_view = View(UItem('plot', editor=ComponentEditor()),
                       width=1000, height=800, resizable=True,)

    def __init__(self, **kw):
        super(TestPlot, self).__init__(**kw)

        plot_data = ArrayPlotData(x=list(xrange(0, 7000)), y=[150] * 7000)
        self.plot = Plot(plot_data)    
        self.plot.plot(('x', 'y'), type='bar', line_color="gray", fill_color="lightgray")

        self.plot.index_mapper.range.set(low=0 - 150, high=8000 + 50)
        self.plot.value_mapper.range.set(low=0 - 50, high=100 + 100)


test = TestPlot()

if __name__ == "__main__":
    test.configure_traits()