--- i/lisp/progmodes/python.el
+++ w/lisp/progmodes/python.el
@@ -3399,24 +3399,30 @@ python-shell-completion-native-setup
                 instance.rlcomplete = new_completer
 
         if readline.__doc__ and 'libedit' in readline.__doc__:
-            readline.parse_and_bind('bind ^I rl_complete')
+            # readline.parse_and_bind('bind ^I rl_complete')
+            print ('libedit not supported')
         else:
             readline.parse_and_bind('tab: complete')
             # Require just one tab to send output.
             readline.parse_and_bind('set show-all-if-ambiguous on')
+            print ('python.el: native completion setup loaded')
 
-        print ('python.el: native completion setup loaded')
     except:
         print ('python.el: native completion setup failed')
 
 __PYTHON_EL_native_completion_setup()" process)
-      (when (and
-             (python-shell-accept-process-output
-              process python-shell-completion-native-try-output-timeout)
-             (save-excursion
-               (re-search-backward
-                (regexp-quote "python.el: native completion setup loaded") nil t 1)))
-        (python-shell-completion-native-try)))))
+      (when (python-shell-accept-process-output
+             process python-shell-completion-native-try-output-timeout)
+        (cond ((save-excursion
+                 (re-search-backward
+                  (regexp-quote "python.el: native completion setup loaded") nil t 1))
+               (python-shell-completion-native-try))
+              ((save-excursion (search-backward "libedit" nil t 1))
+               (lwarn '(python libedit)
+                      :error "\
+Your `python-shell-interpreter' uses a libedit based readline
+module which is currently not supported.")
+               nil))))))
 
 (defun python-shell-completion-native-turn-off (&optional msg)
   "Turn off shell native completions.