SubplotBase._make_twin_axes always creates a new subplot instance. Fixes matplotlib#1957.

Author: leejjoon

lib/matplotlib/axes.py

@@ -9062,7 +9062,14 @@ def _make_twin_axes(self, *kl, **kwargs):
         """
         make a twinx axes of self. This is used for twinx and twiny.
         """
-        ax2 = self.figure.add_subplot(self.get_subplotspec(), *kl, **kwargs)
+        from matplotlib.projections import process_projection_requirements
+        kl = (self.get_subplotspec(),) + kl
+        projection_class, kwargs, key = process_projection_requirements(
+            self.figure, *kl, **kwargs)
+
+        ax2 = subplot_class_factory(projection_class)(self.figure,
+                                                      *kl, **kwargs)
+        self.figure.add_subplot(ax2)
         return ax2