diff --git a/package/osx/installer.js b/package/osx/installer.js
index b445a497..bbdceebc 100644
--- a/package/osx/installer.js
+++ b/package/osx/installer.js
@@ -103,7 +103,7 @@ function checkFilePath(path, ext) {
     if (!path) {
         throw 'File not specified: ' + ext;
     }
-    if (!path.endsWith('.' + ext)) {
+    if (path.substr(-(ext.length + 1)) !== '.' + ext) {
         throw 'Bad file extension: ' + ext + ' (' + path + ')';
     }
     var file = Application('System Events').files.byName(path);