diff --git a/hledger/hledger.m4.md b/hledger/hledger.m4.md
index b3aba2af9..271aeb46a 100644
--- a/hledger/hledger.m4.md
+++ b/hledger/hledger.m4.md
@@ -534,6 +534,7 @@ If they're not doing what you expect, it's important to know exactly what they s
    can be used in the replacement string to reference [capturing groups] in the
    search regexp. Otherwise, if you write `\1`, it will match the digit `1`.
 6. they do not support [mode modifiers] (`(?s)`), character classes (`\w`, `\d`), or anything else not mentioned above.
+7. they may not (I'm guessing not) properly support right-to-left or bidirectional text.
 
 [POSIX ERE]: http://www.regular-expressions.info/posix.html#ere
 [backreferences]: https://www.regular-expressions.info/backref.html