diff --git a/IPython/terminal/interactiveshell.py b/IPython/terminal/interactiveshell.py
index 0fa9028..2714412 100644
--- a/IPython/terminal/interactiveshell.py
+++ b/IPython/terminal/interactiveshell.py
@@ -204,9 +204,8 @@ class TerminalInteractiveShell(InteractiveShell):
 
     @observe('editing_mode')
     def _editing_mode(self, change):
-        u_mode = change.new.upper()
         if self.pt_app:
-            self.pt_app.editing_mode = u_mode
+            self.pt_app.editing_mode = getattr(EditingMode, change.new.upper())
 
     @observe('autoformatter')
     def _autoformatter_changed(self, change):