matplotlib
diff --git a/‎lib/matplotlib/colorbar.py
Lines changed: 2 additions & 0 deletions b/‎lib/matplotlib/colorbar.py
Lines changed: 2 additions & 0 deletions
diff --git a/‎lib/matplotlib/colors.py
Lines changed: 7 additions & 6 deletions b/‎lib/matplotlib/colors.py
Lines changed: 7 additions & 6 deletions
diff --git a/‎lib/matplotlib/tests/test_colors.py
Lines changed: 4 additions & 0 deletions b/‎lib/matplotlib/tests/test_colors.py
Lines changed: 4 additions & 0 deletions
@@ -430,6 +430,8 @@ def __init__(self, ax, cmap=None,
             cmap = cm.get_cmap()
         if norm is None:
             norm = colors.Normalize()
+        elif hasattr(norm, 'extend') and norm.extend != 'neither':
+            extend = norm.extend
         self.alpha = alpha
         self.cmap = cmap
         self.norm = norm
 
@@ -1439,6 +1439,9 @@ def __init__(self, boundaries, ncolors, clip=False, extend='neither'):
         If the number of bins doesn't equal *ncolors*, the color is chosen
         by linear interpolation of the bin number onto color numbers.
         """
+
+        if clip and extend != 'neither':
+            raise ValueError("'clip=True' is not compatible with 'extend'")
         self.clip = clip
         self.vmin = boundaries[0]
         self.vmax = boundaries[-1]
@@ -1447,20 +1450,18 @@ def __init__(self, boundaries, ncolors, clip=False, extend='neither'):
         self.Ncmap = ncolors
 
         # Extension. We use the same trick as colorbar.py and add a fake
-        # boundary were needed. Since colorbar does it too, we have to use a
-        #  private property for that.
+        # boundary were needed.
         _b = list(boundaries)
         if extend == 'both':
             _b = [_b[0] - 1] + _b + [_b[-1] + 1]
         elif extend == 'min':
             _b = [_b[0] - 1] + _b
         elif extend == 'max':
             _b = _b + [_b[-1] + 1]
-        self._b = np.array(_b)
+        self.extend = extend
 
-        # I am not sure if the private _N is necessary (I dont think so,
-        # but it should be consistent with boundaries I guess. This _N is
-        # used for interpolation).
+        # needed for the interpolation but should not be seen from outside
+        self._b = np.array(_b)
         self._N = len(self._b)
         if self._N - 1 == self.Ncmap:
             self._interp = False
 
@@ -296,6 +296,10 @@ def test_BoundaryNorm():
     np.testing.assert_array_equal(1, mynorm(1.1))
     np.testing.assert_array_equal(4, mynorm(12))
 
+    # Test raises
+    assert_raises(ValueError, mcolors.BoundaryNorm, bounds, cmref.N,
+                  extend='both', clip=True)
+
     # Just min
     cmref = mcolors.ListedColormap(['blue', 'red'])
     cmref.set_under('white')