diff --git a/lib/6to5/transformation/modules/common.js b/lib/6to5/transformation/modules/common.js
index c577052740..77224cd148 100644
--- a/lib/6to5/transformation/modules/common.js
+++ b/lib/6to5/transformation/modules/common.js
@@ -71,7 +71,7 @@ CommonJSFormatter.prototype.exportDeclaration = function (node, nodes) {
     // exports = module.exports = VALUE;
     if (this.hasNonDefaultExports) templateName = "exports-default-module-override";
 
-    if (t.isFunction(declar) || !this.hasNonDefaultExports) {
+    if (t.isFunctionDeclaration(declar) || !this.hasNonDefaultExports) {
       assign = util.template(templateName, {
         VALUE: this._pushStatement(declar, nodes)
       }, true);