diff --git a/src/js/pages/nav.js b/src/js/pages/nav.js
index 16f2e78..abaf6b3 100644
--- a/src/js/pages/nav.js
+++ b/src/js/pages/nav.js
@@ -118,7 +118,7 @@ const initModalDialog = (breakpoint) => {
     Object.assign(menu, {
       role: 'dialog',
       ariaModal: 'true',
-      tabindex: '-1'
+      tabIndex: '-1'
     });
   } else {
     ['role', 'aria-modal', 'tabindex'].forEach(attr => {