diff --git a/src/helpers.js b/src/helpers.js
index cb62211..7748cd8 100644
--- a/src/helpers.js
+++ b/src/helpers.js
@@ -8,7 +8,7 @@ export function commonjsRequire () {
 }
 
 export function unwrapExports (x) {
-	return x && x.__esModule ? x['default'] : x;
+	return x && x.__esModule && Object.prototype.hasOwnProperty.call(x, 'default') ? x['default'] : x;
 }
 
 export function createCommonjsModule(fn, module) {
diff --git a/test/samples/use-own-output/from-rollup.js b/test/samples/use-own-output/from-rollup.js
new file mode 100644
index 0000000..3a0bcda
--- /dev/null
+++ b/test/samples/use-own-output/from-rollup.js
@@ -0,0 +1,2 @@
+Object.defineProperty(exports, '__esModule', { value: true });
+exports.x = 10
diff --git a/test/samples/use-own-output/main.js b/test/samples/use-own-output/main.js
new file mode 100644
index 0000000..c011220
--- /dev/null
+++ b/test/samples/use-own-output/main.js
@@ -0,0 +1,2 @@
+import * as b from "./from-rollup";
+window.b = b;
diff --git a/test/test.js b/test/test.js
index 074c357..cb581f4 100644
--- a/test/test.js
+++ b/test/test.js
@@ -420,5 +420,17 @@ describe( 'rollup-plugin-commonjs', () => {
 			assert.notEqual( code.indexOf( 'var validVar' ), -1 );
 			assert.notEqual( code.indexOf( 'var nonIndex' ), -1 );
 		});
+
+		it( 'does not misassign default when consuming rollup output', async () => {
+			// Issue #224
+			const bundle = await rollup({
+				entry: 'samples/use-own-output/main.js',
+				plugins: [ commonjs() ],
+			});
+
+			const window = {};
+			await executeBundle( bundle, { context: { window } } );
+			assert.notEqual( window.b.default, undefined );
+		});
 	});
 });