diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9de8113..dc0a7ee 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Bug Fixes
+
+- fix: Centre the text of the highlighted-lines chip vertically in browsers that support `text-box`. (#86)
+
 ## 1.8.1 (2026-11-05)
 
 ### Bug Fixes
diff --git a/_extensions/code-window/style.css b/_extensions/code-window/style.css
index c739eb2..c4f886d 100644
--- a/_extensions/code-window/style.css
+++ b/_extensions/code-window/style.css
@@ -95,6 +95,16 @@ body.quarto-dark .code-with-filename .code-with-filename-file {
   overflow-wrap: break-word;
 }
 
+/* The line box keeps room for descenders that a label such as "L1-3" does not
+ * have. Trim it to the cap height and the baseline, so the padding alone sets
+ * the space above and below the text. */
+@supports (text-box: trim-both cap alphabetic) {
+  .code-with-filename .code-with-filename-file .code-with-filename-lines {
+    padding-block: 0.3em;
+    text-box: trim-both cap alphabetic;
+  }
+}
+
 /* Code block content area */
 .code-with-filename .sourceCode,
 .code-with-filename div.sourceCode,