diff --git a/lib/matplotlib/tests/test_pickle.py b/lib/matplotlib/tests/test_pickle.py
index cab412bff561..7e7ccc14bf8f 100644
--- a/lib/matplotlib/tests/test_pickle.py
+++ b/lib/matplotlib/tests/test_pickle.py
@@ -15,7 +15,7 @@
 import matplotlib.pyplot as plt
 import matplotlib.transforms as mtransforms
 import matplotlib.figure as mfigure
-from mpl_toolkits.axes_grid1 import parasite_axes  # type: ignore
+from mpl_toolkits.axes_grid1 import axes_divider, parasite_axes  # type: ignore
 
 
 def test_simple():
@@ -274,6 +274,7 @@ def test_unpickle_canvas():
 
 def test_mpl_toolkits():
     ax = parasite_axes.host_axes([0, 0, 1, 1])
+    axes_divider.make_axes_area_auto_adjustable(ax)
     assert type(pickle.loads(pickle.dumps(ax))) == parasite_axes.HostAxes
 
 
diff --git a/lib/mpl_toolkits/axes_grid1/axes_size.py b/lib/mpl_toolkits/axes_grid1/axes_size.py
index d25147207726..e417c1a899ac 100644
--- a/lib/mpl_toolkits/axes_grid1/axes_size.py
+++ b/lib/mpl_toolkits/axes_grid1/axes_size.py
@@ -233,14 +233,14 @@ class _AxesDecorationsSize(_Base):
     }
 
     def __init__(self, ax, direction):
-        self._get_size = _api.check_getitem(
-            self._get_size_map, direction=direction)
+        _api.check_in_list(self._get_size_map, direction=direction)
+        self._direction = direction
         self._ax_list = [ax] if isinstance(ax, Axes) else ax
 
     def get_size(self, renderer):
         sz = max([
-            self._get_size(ax.get_tightbbox(renderer, call_axes_locator=False),
-                           ax.bbox)
+            self._get_size_map[self._direction](
+                ax.get_tightbbox(renderer, call_axes_locator=False), ax.bbox)
             for ax in self._ax_list])
         dpi = renderer.points_to_pixels(72)
         abs_size = sz / dpi