diff --git a/IPython/terminal/prompts.py b/IPython/terminal/prompts.py
index db1b751..ee2c5d7 100644
--- a/IPython/terminal/prompts.py
+++ b/IPython/terminal/prompts.py
@@ -7,6 +7,7 @@ from IPython.core.displayhook import DisplayHook
 
 from prompt_toolkit.formatted_text import fragment_list_width, PygmentsTokens
 from prompt_toolkit.shortcuts import print_formatted_text
+from prompt_toolkit.enums import EditingMode
 
 
 class Prompts(object):
@@ -14,7 +15,7 @@ class Prompts(object):
         self.shell = shell
 
     def vi_mode(self):
-        if (getattr(self.shell.pt_app, 'editing_mode', None) == 'VI'
+        if (getattr(self.shell.pt_app, 'editing_mode', None) == EditingMode.VI
                 and self.shell.prompt_includes_vi_mode):
             return '['+str(self.shell.pt_app.app.vi_state.input_mode)[3:6]+'] '
         return ''