diff --git a/Developing-Regex-in-Fail2ban.md b/Developing-Regex-in-Fail2ban.md
index f3e1867..6418341 100644
--- a/Developing-Regex-in-Fail2ban.md
+++ b/Developing-Regex-in-Fail2ban.md
@@ -40,6 +40,8 @@ Date template hits:
 ```
 Note the '`[6]`' output which matches my examples given in the next top-level section below.
 
+Important note: if your date pattern use %b or %B beware of checking you are in the right locale ! (your terminal might set a different locale than the server default). (use `locale -a` and `export LANG=xxx` to fix this).
+
 Pre-Filtering
 -------------
 After clearing/setting the `prefregex`, test it again and watch for `Pre-filter matched` in your output: