diff --git a/lib/index.js b/lib/index.js
index 46ad49c6..f8cde9e4 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -6,6 +6,8 @@
 
 if (typeof Realm != 'undefined') {
     module.exports = Realm;  // eslint-disable-line no-undef
-} else {
+} else if (navigator.userAgent) {
     module.exports = require('./realm');
+} else {
+    throw new Error('Missing Realm constructor - please ensure RealmReact framework is included!');
 }