diff --git a/graal-nodejs/src/node_url.cc b/graal-nodejs/src/node_url.cc
index 149a926841b..4d3c8108fa6 100644
--- a/graal-nodejs/src/node_url.cc
+++ b/graal-nodejs/src/node_url.cc
@@ -168,7 +168,7 @@ void BindingData::Format(const FunctionCallbackInfo<Value>& args) {
     out->hash = std::nullopt;
   }
 
-  if (unicode) {
+  if (unicode && out->has_hostname()) {
     out->host = ada::idna::to_unicode(out->get_hostname());
   }
 
diff --git a/graal-nodejs/test/parallel/test-url-format-whatwg.js b/graal-nodejs/test/parallel/test-url-format-whatwg.js
index d1f0e0bcbdd..bf9f8eaac63 100644
--- a/graal-nodejs/test/parallel/test-url-format-whatwg.js
+++ b/graal-nodejs/test/parallel/test-url-format-whatwg.js
@@ -140,3 +140,8 @@ assert.strictEqual(
   url.format(new URL('http://user:pass@xn--0zwm56d.com:8080/path'), { unicode: true }),
   'http://user:pass@测试.com:8080/path'
 );
+
+assert.strictEqual(
+  url.format(new URL('tel:123')),
+  url.format(new URL('tel:123'), { unicode: true })
+);