diff --git a/js/src/u2f.js b/js/src/u2f.js
index 17af42f767..dea3c6bbe8 100644
--- a/js/src/u2f.js
+++ b/js/src/u2f.js
@@ -8,6 +8,11 @@ AJAX.registerOnload('u2f.js', function () {
         setTimeout(function () {
             // A magic JS function that talks to the USB device. This function will keep polling for the USB device until it finds one.
             var request = JSON.parse($inputReg.attr('data-request'));
+
+            if (!(window.u2f && typeof window.u2f.register === 'function')) {
+                return;
+            }
+
             u2f.register(request.appId, [request], JSON.parse($inputReg.attr('data-signatures')), function (data) {
                 // Handle returning error data
                 if (data.errorCode && data.errorCode !== 0) {
@@ -45,6 +50,11 @@ AJAX.registerOnload('u2f.js', function () {
             // Magic JavaScript talking to your HID
             // appid, challenge, authenticateRequests
             var request = JSON.parse($inputAuth.attr('data-request'));
+
+            if (!(window.u2f && typeof window.u2f.sign === 'function')) {
+                return;
+            }
+
             u2f.sign(request[0].appId, request[0].challenge, request, function (data) {
                 // Handle returning error data
                 if (data.errorCode && data.errorCode !== 0) {