matplotlib
diff --git a/‎lib/matplotlib/colorbar.py
Copy file name to clipboardExpand all lines: lib/matplotlib/colorbar.py
+3-2Lines changed: 3 additions & 2 deletions b/‎lib/matplotlib/colorbar.py
Copy file name to clipboardExpand all lines: lib/matplotlib/colorbar.py
+3-2Lines changed: 3 additions & 2 deletions
diff --git a/‎lib/matplotlib/tests/test_colorbar.py
Copy file name to clipboardExpand all lines: lib/matplotlib/tests/test_colorbar.py
+9-1Lines changed: 9 additions & 1 deletion b/‎lib/matplotlib/tests/test_colorbar.py
Copy file name to clipboardExpand all lines: lib/matplotlib/tests/test_colorbar.py
+9-1Lines changed: 9 additions & 1 deletion
@@ -828,8 +828,9 @@ def _process_values(self, b=None):
 
             b = self.norm.inverse(self._uniform_y(self.cmap.N + 1))
 
-            if isinstance(self.norm, colors.LogNorm):
-                # If using a lognorm, ensure extensions don't go negative
+            if isinstance(self.norm, (colors.PowerNorm, colors.LogNorm)):
+                # If using a lognorm or powernorm, ensure extensions don't
+                # go negative
                 if self._extend_lower():
                     b[0] = 0.9 * b[0]
                 if self._extend_upper():
 
@@ -4,7 +4,7 @@
 from matplotlib import rc_context
 from matplotlib.testing.decorators import image_comparison
 import matplotlib.pyplot as plt
-from matplotlib.colors import BoundaryNorm, LogNorm
+from matplotlib.colors import BoundaryNorm, LogNorm, PowerNorm
 from matplotlib.cm import get_cmap
 from matplotlib.colorbar import ColorbarBase
 
@@ -372,6 +372,14 @@ def test_colorbar_lognorm_extension():
     assert cb._values[0] >= 0.0
 
 
+def test_colorbar_powernorm_extension():
+    # Test that colorbar with powernorm is extended correctly
+    f, ax = plt.subplots()
+    cb = ColorbarBase(ax, norm=PowerNorm(gamma=0.5, vmin=0.0, vmax=1.0),
+                      orientation='vertical', extend='both')
+    assert cb._values[0] >= 0.0
+
+
 def test_colorbar_axes_kw():
     # test fix for #8493: This does only test, that axes-related keywords pass
     # and do not raise an exception.