diff --git a/doc/manual/custom.css b/doc/manual/custom.css
index 69d48d4a7..b90f5423f 100644
--- a/doc/manual/custom.css
+++ b/doc/manual/custom.css
@@ -5,3 +5,7 @@ h1:not(:first-of-type) {
 h2 {
     margin-top: 1em;
 }
+
+.hljs-meta {
+    user-select: none;
+}