diff --git a/src/transform.js b/src/transform.js
index 9f731c5..88238d0 100644
--- a/src/transform.js
+++ b/src/transform.js
@@ -109,7 +109,7 @@ export default function transform ( code, id, isEntry, ignoreGlobal, customNamed
 
 				// we're dealing with `module.exports = ...` or `[module.]exports.foo = ...` –
 				// if this isn't top-level, we'll need to wrap the module
-				if ( programDepth > 3 ) shouldWrap = true;
+				if ( programDepth > 3 || /^Function/.test( node.right.type )) shouldWrap = true;
 
 				node.left._skip = true;
 
diff --git a/test/form/optimised-default-export-function/output.js b/test/form/optimised-default-export-function/output.js
index bfb9a41..c9d5d01 100644
--- a/test/form/optimised-default-export-function/output.js
+++ b/test/form/optimised-default-export-function/output.js
@@ -1,4 +1,8 @@
-var input = function foo () {};
+import * as commonjsHelpers from 'commonjsHelpers';
+
+var input = commonjsHelpers.createCommonjsModule(function (module) {
+module.exports = function foo () {};
+});
 
 export default input;
 export { input as __moduleExports };