diff --git a/app/views/wallet/index.html.erb b/app/views/wallet/index.html.erb
index 5e6e1f5..ddcc8b7 100644
--- a/app/views/wallet/index.html.erb
+++ b/app/views/wallet/index.html.erb
@@ -37,23 +37,25 @@
 </section>
 
 <script type="text/javascript">
-  let linkShow = document.querySelector('#show-setup-code');
-  let linkHide = document.querySelector('#hide-setup-code');
-  let setupCode = document.querySelector('#setup-code');
+  (function () {
+    const linkShow = document.querySelector('#show-setup-code');
+    const linkHide = document.querySelector('#hide-setup-code');
+    const setupCode = document.querySelector('#setup-code');
 
-  linkShow.addEventListener('click', function(ev) {
-    ev.preventDefault();
-    setupCode.style.display = 'block';
-    linkShow.style.display = 'none';
-    linkHide.style.display = 'block';
-    window.scrollTo(0, document.body.scrollHeight);
-  });
+    linkShow.addEventListener('click', function(ev) {
+      ev.preventDefault();
+      setupCode.style.display = 'block';
+      linkShow.style.display = 'none';
+      linkHide.style.display = 'block';
+      window.scrollTo(0, document.body.scrollHeight);
+    });
 
-  linkHide.addEventListener('click', function(ev) {
-    ev.preventDefault();
-    const el = document.querySelector('#setup-code');
-    setupCode.style.display = 'none';
-    linkShow.style.display = 'block';
-    linkHide.style.display = 'none';
-  });
+    linkHide.addEventListener('click', function(ev) {
+      ev.preventDefault();
+      const el = document.querySelector('#setup-code');
+      setupCode.style.display = 'none';
+      linkShow.style.display = 'block';
+      linkHide.style.display = 'none';
+    });
+  })();
 </script>