diff --git a/src/utils.ts b/src/utils.ts
index 159ce1844..cae4164d1 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -17,7 +17,7 @@ export const safePackageName = (name: string) =>
   name.toLowerCase().replace(/((^[^a-zA-Z]+)|[^\w.-])|([^a-zA-Z0-9]+$)/g, '');
 
 export const external = (id: string) =>
-  !id.startsWith('.') && !id.startsWith('/');
+  !id.startsWith('.') && !path.isAbsolute(id);
 
 // Make sure any symlinks in the project folder are resolved:
 // https://github.com/facebookincubator/create-react-app/issues/637
diff --git a/test/fixtures/build-default/src/foo.ts b/test/fixtures/build-default/src/foo.ts
new file mode 100644
index 000000000..0abb9556d
--- /dev/null
+++ b/test/fixtures/build-default/src/foo.ts
@@ -0,0 +1 @@
+export const foo = () => 'bar';
diff --git a/test/fixtures/build-default/src/index.ts b/test/fixtures/build-default/src/index.ts
index af27ae37d..b23b6213f 100644
--- a/test/fixtures/build-default/src/index.ts
+++ b/test/fixtures/build-default/src/index.ts
@@ -1,3 +1,5 @@
+export { foo } from './foo';
+
 export const sum = (a: number, b: number) => {
   if ('development' === process.env.NODE_ENV) {
     console.log('fuck');
diff --git a/test/tests/tsdx-build.test.js b/test/tests/tsdx-build.test.js
index 6766ee66c..98c267f17 100644
--- a/test/tests/tsdx-build.test.js
+++ b/test/tests/tsdx-build.test.js
@@ -42,6 +42,15 @@ describe('tsdx build', () => {
     expect(output.code).toBe(0);
   });
 
+  it('should create the library correctly', () => {
+    util.setupStageWithFixture(stageName, 'build-default');
+
+    shell.exec('node ../dist/index.js build');
+
+    const lib = require(`../../${stageName}/dist`);
+    expect(lib.foo()).toBe('bar');
+  });
+
   afterEach(() => {
     util.teardownStage(stageName);
   });