diff --git a/examples/typescript-node-es6/src/index.ts b/examples/typescript-node-es6/src/index.ts
index bb3792485..7b28a0c28 100644
--- a/examples/typescript-node-es6/src/index.ts
+++ b/examples/typescript-node-es6/src/index.ts
@@ -7,6 +7,8 @@ const source = `<xml xmlns="a">
 
 const doc = new DOMParser().parseFromString(source, 'text/xml')
 
+if (!doc) throw 'expected Document but was null'
+
 const serialized = new XMLSerializer().serializeToString(doc)
 
 if (source !== serialized) {