diff --git a/lib/6to5/transformation/modules/umd.js b/lib/6to5/transformation/modules/umd.js
index 1a502a24a1..299a4aee22 100644
--- a/lib/6to5/transformation/modules/umd.js
+++ b/lib/6to5/transformation/modules/umd.js
@@ -39,8 +39,8 @@ UMDFormatter.prototype.transform = function (ast) {
   defineArgs = [t.arrayExpression(defineArgs)];
 
   // typeof exports !== "undefined" && typeof module !== "undefined"
-  var testExports = t.binaryExpression("!==", t.typeOfExpression(t.identifier("exports")), t.literal("undefined")),
-      testModule = t.binaryExpression("!==", t.typeOfExpression(t.identifier("module")), t.literal("undefined")),
+  var testExports = t.binaryExpression("!==", t.unaryExpression("typeof", t.identifier("exports"), true), t.literal("undefined")),
+      testModule = t.binaryExpression("!==", t.unaryExpression("typeof", t.identifier("module"), true), t.literal("undefined")),
       commonTests = this.passModuleArg ? t.logicalExpression("&&", testExports, testModule) : testExports;
 
   var commonArgs = [t.identifier("exports")];