diff --git a/tests/karma-test-main.js b/tests/karma-test-main.js
index b3538046..657e3121 100644
--- a/tests/karma-test-main.js
+++ b/tests/karma-test-main.js
@@ -1,8 +1,8 @@
-const TEST_REGEXP = /test\..*\.js/;
-const allTestFiles = [];
-const extraFiles = ['/base/tests/assertions.js'];
+var TEST_REGEXP = /test\..*\.js/;
+var allTestFiles = [];
+var extraFiles = ['/base/tests/assertions.js'];
 
-Object.keys(window.__karma__.files).forEach((file) => {
+Object.keys(window.__karma__.files).forEach(function (file) {
     if (TEST_REGEXP.test(file)) {
         // TODO: normalize?
         allTestFiles.push(file);