diff --git a/user/book.js b/user/book.js
index f2516be7a..ff3650eb4 100644
--- a/user/book.js
+++ b/user/book.js
@@ -179,7 +179,7 @@ function playground_text(playground, hidden = true) {
     // even if highlighting doesn't apply
     code_nodes.forEach(function (block) { block.classList.add('hljs'); });
 
-    Array.from(document.querySelectorAll("code.language-rust")).forEach(function (block) {
+    Array.from(document.querySelectorAll("code.hljs")).forEach(function (block) {
 
         var lines = Array.from(block.querySelectorAll('.boring'));
         // If no lines were hidden, return