diff --git a/lib/matplotlib/widgets.py b/lib/matplotlib/widgets.py
index f9e8321d8bff..f8d1c47ce0e6 100644
--- a/lib/matplotlib/widgets.py
+++ b/lib/matplotlib/widgets.py
@@ -503,16 +503,21 @@ class CheckButtons(AxesWidget):
 
     Connect to the CheckButtons with the :meth:`on_clicked` method
     """
-    def __init__(self, ax, labels, actives):
+    def __init__(self, ax, labels, actives=None):
         """
         Add check buttons to :class:`matplotlib.axes.Axes` instance *ax*
 
-        *labels*
-            A len(buttons) list of labels as strings
+        Parameters
+        ----------
+        ax : `~matplotlib.axes.Axes`
+            The parent axes for the widget.
+
+        labels : List[str]
+            The labels of the check buttons.
 
-        *actives*
-            A len(buttons) list of booleans indicating whether
-             the button is active
+        actives : List[bool], optional
+            The initial check states of the buttons. The list must have the
+            same length as *labels*. If not given, all buttons are unchecked.
         """
         AxesWidget.__init__(self, ax)
 
@@ -520,6 +525,9 @@ def __init__(self, ax, labels, actives):
         ax.set_yticks([])
         ax.set_navigate(False)
 
+        if actives is None:
+            actives = [False] * len(labels)
+
         if len(labels) > 1:
             dy = 1. / (len(labels) + 1)
             ys = np.linspace(1 - dy, dy, len(labels))
@@ -527,7 +535,6 @@ def __init__(self, ax, labels, actives):
             dy = 0.25
             ys = [0.5]
 
-        cnt = 0
         axcolor = ax.get_facecolor()
 
         self.labels = []
@@ -536,13 +543,13 @@ def __init__(self, ax, labels, actives):
 
         lineparams = {'color': 'k', 'linewidth': 1.25,
                       'transform': ax.transAxes, 'solid_capstyle': 'butt'}
-        for y, label in zip(ys, labels):
+        for y, label, active in zip(ys, labels, actives):
             t = ax.text(0.25, y, label, transform=ax.transAxes,
                         horizontalalignment='left',
                         verticalalignment='center')
 
-            w, h = dy / 2., dy / 2.
-            x, y = 0.05, y - h / 2.
+            w, h = dy / 2, dy / 2
+            x, y = 0.05, y - h / 2
 
             p = Rectangle(xy=(x, y), width=w, height=h, edgecolor='black',
                           facecolor=axcolor, transform=ax.transAxes)
@@ -550,15 +557,14 @@ def __init__(self, ax, labels, actives):
             l1 = Line2D([x, x + w], [y + h, y], **lineparams)
             l2 = Line2D([x, x + w], [y, y + h], **lineparams)
 
-            l1.set_visible(actives[cnt])
-            l2.set_visible(actives[cnt])
+            l1.set_visible(active)
+            l2.set_visible(active)
             self.labels.append(t)
             self.rectangles.append(p)
             self.lines.append((l1, l2))
             ax.add_patch(p)
             ax.add_line(l1)
             ax.add_line(l2)
-            cnt += 1
 
         self.connect_event('button_press_event', self._clicked)