diff --git a/changelog.md b/changelog.md
index 120750c..428472f 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,8 @@
 # Changes in HEAD
 
+- Document `$ZSH_HIGHLIGHT_MAXLENGTH`.
+  [#698]
+
 - Redirection operators (e.g., `<` and `>`) are now highlighted by default
   [#646]