diff --git a/.gitignore b/.gitignore
index ad46b30..9972163 100644
--- a/.gitignore
+++ b/.gitignore
@@ -35,6 +35,7 @@ build/Release
 # Dependency directories
 node_modules/
 jspm_packages/
+package-lock.json
 
 # TypeScript v1 declaration files
 typings/
diff --git a/index.js b/index.js
index 7c8d3a5..48c8e2f 100644
--- a/index.js
+++ b/index.js
@@ -1,7 +1,7 @@
 import { useEffect, useRef, useState, useCallback } from 'react';
 
 // Edge has a bug where scrollHeight is 1px bigger than clientHeight when there's no scroll.
-const isEdge = typeof navigator !== 'undefined' && /Edge\/\d./i.test(window.navigator.userAgent);
+const isEdge = typeof navigator !== 'undefined' && /Edge\/\d./i.test(navigator.userAgent);
 
 // Small hook to use ResizeOberver if available. This fixes some issues when the component is resized.
 // This needs a polyfill to work on all browsers. The polyfill is not included in order to keep the package light.