diff --git a/Doc/library/readline.rst b/Doc/library/readline.rst
index 43cf8d5cdac544..f02aec8a6a8105 100644
--- a/Doc/library/readline.rst
+++ b/Doc/library/readline.rst
@@ -44,6 +44,10 @@ Readline library in general.
     python:bind -v
     python:bind ^I rl_complete
 
+  Also note that different libraries may use different history file formats.
+  When switching the underlying library, existing history files may become
+  unusable.
+
 
 Init file
 ---------