diff --git a/test/index.js b/test/index.js
index e60378c..6800a34 100644
--- a/test/index.js
+++ b/test/index.js
@@ -15,7 +15,7 @@ function makeStubDocument(doctype) {
 
 test('should return empty string if absent', t => {
     const doctype = ''
-    const doc = makeStubDocument()
+    const doc = makeStubDocument(doctype)
     t.is(doctypeToString(doc.doctype), doctype)
 })