diff --git a/src/theme/book.js b/src/theme/book.js
index 328151ca..186f9ae1 100644
--- a/src/theme/book.js
+++ b/src/theme/book.js
@@ -16,9 +16,6 @@ function playpen_text(playpen) {
 }
 
 (function codeSnippets() {
-    // Hide Rust code lines prepended with a specific character
-    var hiding_character = "#";
-
     function fetch_with_timeout(url, options, timeout = 6000) {
         return Promise.race([
             fetch(url, options),