matplotlib · x-meowzilla · Feb 15, 2018 · Feb 15, 2018 · Feb 16, 2018 · Feb 16, 2018
diff --git a/lib/matplotlib/projections/polar.py b/lib/matplotlib/projections/polar.py
@@ -858,6 +858,19 @@ def __init__(self, *args, **kwargs):
         self.cla()
     __init__.__doc__ = Axes.__init__.__doc__
 
+    def add_patch(self, patch):
+        """
+        Override the existing add_patch() method from _AxesBase class.
+        The _interpolation_steps field should be revised prior to drawing.
+
+        :param patch: `~matplotlib.patches.Patch`
+        :return: `~matplotlib.patches.Patch`
+        """
+        patch.get_path()._interpolation_steps = \
+            max(patch.get_path()._interpolation_steps,  # default 1
+                maxis.GRIDLINE_INTERPOLATION_STEPS)  # 180
+        return super().add_patch(patch)
+
     def cla(self):
         Axes.cla(self)
 

diff --git a/lib/matplotlib/tests/baseline_images/test_patches/transform_rectangle.png b/lib/matplotlib/tests/baseline_images/test_patches/transform_rectangle.png
diff --git a/lib/matplotlib/tests/test_patches.py b/lib/matplotlib/tests/test_patches.py
@@ -363,6 +363,17 @@ def test_connection_patch():
     ax2.add_artist(con)
 
 
+@image_comparison(baseline_images=['transform_rectangle'], extensions=['png'],
+                  style='mpl20', remove_text=True)
+def test_polar_rectangle_transform_patch():
+    # Rectangle patch not transformed correctly in polar plot (#8521)
+    rectangle = mpatches.Rectangle((0, 1), width=np.pi * 0.5, height=1)
+    fig = plt.figure(figsize=(6, 8))
+    ax = fig.add_subplot(1, 1, 1, polar=True)
+    ax.add_patch(rectangle)
+    ax.set_rmax(2.5)
+
+
 def test_datetime_rectangle():
     # Check that creating a rectangle with timedeltas doesn't fail
     from datetime import datetime, timedelta