diff --git a/tools/build-test.js b/tools/build-test.js
index 8b4d0aa..a2a407b 100644
--- a/tools/build-test.js
+++ b/tools/build-test.js
@@ -6,6 +6,9 @@ var babelify = require('babelify')
 browserify()
   .exclude(['citation-js'])
   .add('./test/wrapper.js')
-  .transform(babelify, {global: true})
+  .transform(babelify, {
+    global: true,
+    ignore: ['node_modules/expect.js/']
+  })
   .bundle()
   .pipe(fs.createWriteStream(path.join(__dirname, '../build/test.citation.js')))