diff --git a/lib/matplotlib/backends/backend_nbagg.py b/lib/matplotlib/backends/backend_nbagg.py
index c2e18955cc1b..16d3d51e0a74 100644
--- a/lib/matplotlib/backends/backend_nbagg.py
+++ b/lib/matplotlib/backends/backend_nbagg.py
@@ -3,8 +3,6 @@
 # lib/matplotlib/backends/web_backend/nbagg_uat.ipynb to help verify
 # that changes made maintain expected behaviour.
 
-import six
-
 from base64 import b64encode
 import io
 import json
@@ -204,9 +202,7 @@ def send_json(self, content):
     def send_binary(self, blob):
         # The comm is ascii, so we always send the image in base64
         # encoded data URL form.
-        data = b64encode(blob)
-        if six.PY3:
-            data = data.decode('ascii')
+        data = b64encode(blob).decode('ascii')
         data_uri = "data:image/png;base64,{0}".format(data)
         self.comm.send({'data': data_uri})
 
diff --git a/lib/matplotlib/backends/backend_webagg_core.py b/lib/matplotlib/backends/backend_webagg_core.py
index ab9f2c3813c4..ab8fda933b98 100644
--- a/lib/matplotlib/backends/backend_webagg_core.py
+++ b/lib/matplotlib/backends/backend_webagg_core.py
@@ -10,11 +10,6 @@
 # - `backend_webagg.py` contains a concrete implementation of a basic
 #   application, implemented with tornado.
 
-from __future__ import (absolute_import, division, print_function,
-                        unicode_literals)
-
-import six
-
 import datetime
 import io
 import json
@@ -26,8 +21,7 @@
 
 from matplotlib.backends import backend_agg
 from matplotlib.backend_bases import _Backend
-from matplotlib import backend_bases
-from matplotlib import _png
+from matplotlib import backend_bases, _png
 
 
 # http://www.cambiaresearch.com/articles/15/javascript-char-codes-key-codes
@@ -150,17 +144,11 @@ def show(self):
         show()
 
     def draw(self):
-        renderer = self.get_renderer(cleared=True)
-
         self._png_is_old = True
-
-        backend_agg.RendererAgg.lock.acquire()
         try:
-            self.figure.draw(renderer)
+            super().draw()
         finally:
-            backend_agg.RendererAgg.lock.release()
-            # Swap the frames
-            self.manager.refresh_all()
+            self.manager.refresh_all()  # Swap the frames.
 
     def draw_idle(self):
         self.send_event("draw")